Efficacy of Popular Diets for WeightLoss and Weight Maintenance in Adults

Item Type text; Electronic Thesis

Authors Fretto, Madelynn Lea

Publisher The University of Arizona.

Rights Copyright © is held by the author. Digital access to this materialis made possible by the University Libraries, University of Arizona.Further transmission, reproduction or presentation (such aspublic display or performance) of protected items is prohibitedexcept with permission of the author.

Download date 20/02/2021 09:49:48

Link to Item http://hdl.handle.net/10150/624986

EFFICACY OF POPULAR DIETS FOR WEIGHT LOSS AND

WEIGHT MAINTENANCE IN ADULTS

By

MADELYNN LEA FRETTO

____________________

A Thesis Submitted to The Honors College

In Partial Fulfillment of the Bachelors degree

With Honors in

Physiology

THE UNIVERSITY OF ARIZONA

M A Y 2 0 1 7

Approved by: ____________________________ Dr. Claudia Stanescu Department of Physiology

TABLE OF CONTENTS  I.  ABSTRACT  ...........................................................................................................................................................  3  II.  INTRODUCTION  ...............................................................................................................................................  3  III.  METHODS  .........................................................................................................................................................  4  IV.  RESULTS  ............................................................................................................................................................  5  IV.  A.  ORLISTAT  .........................................................................................................................................................................  5  IV.  B.  MEAL  REPLACEMENT  PRODUCTS  ............................................................................................................................  12  IV.  C.  MEDIFAST  .....................................................................................................................................................................  22  IV.  D.  BARIATRIC  SURGERY  ..................................................................................................................................................  31  

V.  DISCUSSION  ....................................................................................................................................................  39  REFERENCES  .......................................................................................................................................................  43  

I. Abstract

This review discusses popular diet methods that are advertised as effective options for

people struggling to lose weight. Obesity is a prevalent issue in the United States, which

increases a person’s risk for other comorbidities, notably cardiovascular diseases. This review

seeks to determine the most effective weight loss method by comparing Orlistat, meal

replacement products, Medifast, and bariatric surgery. The studies selected included both male

and female adults (18+ years old) classified as overweight or obese based on their body mass

index (BMI). The results showed that each of the four methods caused weight loss, but not all

sustained this weight loss. Bariatric surgery had the highest percentage weight loss for patients,

which was often sustained for many years after the procedure due to the physiological

manipulation of the digestive system. Though bariatric surgery had the most promising results,

not everyone qualifies for the procedure based on their BMI and other comorbidities. Thus, a

more feasible weight loss and maintenance plan is the Medifast program. This paid program

includes pre-made meals and the option of one-on-one counseling to implement lifestyle changes

that can be used long-term for sustained, healthy weight loss.

II. Introduction

Obesity is a serious issue that is prevalent in the United States, as well as the rest of

the world. Unfortunately, it is associated with numerous health problems and risks, including

heart disease and diabetes.7 About 64% of adults in the United States are considered overweight

or obese.7 Losing weight may seem like a relatively straightforward task, since many

recommendations include more exercise and less food intake. The weight may be seemingly easy

to lose quickly, but weight loss maintenance and avoidance of regaining this weight is the most

difficult part when it comes to dieting. There are many “quick fixes” for dieting that are

  4

advertised in our everyday lives. People are constantly bombarded with the newest weight loss

products that promise the quickest and easiest ways to lose weight. It is a pressure in today’s

society to be fit and skinny. Naturally, with this type of pressure, people often look to the

quickest way to lose weight with the least amount of effort. The purpose of this literature review

is to research the efficacy of four popular diets and weight loss methods in terms of weight loss

and weight loss maintenance. These four diet methods include: 1) Orlistat, an anti-obesity

capsule; 2) meal replacement products, which include drinks or bars to substitute a solid food

meal; 3) Medifast, a paid nutrition and weight loss program; and 4) bariatric surgery, which

physically alters the digestive system. Each of these methods will be analyzed in detail and can

be compared to the others most notably by percentage of weight loss, while also including other

factors including blood pressure and cholesterol changes. The most effective diet method for

weight loss and maintenance is hypothesized to be bariatric surgery, since this surgery alters the

digestive system and can physically reduce the size of the stomach. This usually is a permanent

solution and changes the patient’s eating habits so they are not consuming as much food as they

were before.

III. Methods

The studies selected for this review included overweight and obese adults who were at

least 18 years old. Additionally, the studies included both male and female subjects. Body mass

index (BMI) is used to determine if a subject is overweight or obese. BMI is a commonly used

measurement in the medical field that divides weight (kilograms) by height squared (meters).

BMI is a simple calculation that is used for screening, and a high BMI score often correlates with

high body fat. A healthy person has a BMI of 18.5-24.9 kg/m2. In contrast, a person is considered

overweight if their BMI is 25.0-29.9 kg/m2 and obese if their BMI is 30+ kg/m2.1

  5

IV. Results

IV. A. Orlistat

Orlistat, a pharmacotherapeutic drug intended for weight loss, is considered a

gastrointestinal lipase inhibitor.17 Orlistat is the only drug approved by the FDA that affects food

absorption, distribution, and metabolism.12 Orlistat hinders food digestion and fat absorption in

the GI tract by binding to lipids and impeding the functions of gastric and pancreatic lipases.12,17

Gastrointestinal lipases absorb the triglycerides found in fats people consume while eating, and

promote gastric emptying. Orlistat is a synthetic form of lipstatin, which is a lipase inhibitor that

comes from Streptomyces toxytricini bacteria.17 Orlistat functions by locally decreasing the fat

absorption that normally occurs after eating by selectively inhibiting lipase functions.12,17 By

inhibiting these lipases, lipolysis is decreased, which is hydrolysis of triglycerides, and fat

excretion via feces is increased. Additionally, lipolysis products, free fatty acids, and

monoglycerides are not absorbed as well in the body.12 The drug also decreases absorption of

cholesterol by decreasing the amount of free fatty acids. Through numerous clinical trials, results

showed there was a 30% decrease in GI fat absorption when the approved dosage of Orlistat is

taken.12,17

Orlistat is recommended for adults who are considered obese or they are considered

overweight and they have other risk factors. These risk factors can include high blood pressure,

type 2 diabetes mellitus (DM), sleep apnea, and coronary heart disease (CHD).17 Every meal

must contain fat in order for Orlistat to be effective because Orlistat specifically inhibits the

breakdown of dietary fats. A low dietary fat intake is considered less than 45 grams, so the intake

for each meal should be higher than this. A person’s diet should have less than 67 grams of fat

for 2,000 kcal daily while taking this medication.19 There are two brands of Orlistat, which are

  6

Xenical and Alli, and both are approved for obesity intervention. The usual dosage for Xenical is

120 mg, three times a day, taken with a fat-containing meal or one hour after the meal. For Alli,

the dosage is 60 mg, three times a day, also taken with a fat-containing meal or one hour

afterwards.17

The National Institutes of Health (NIH) has parameters for overweight and obese patients

that must be met in order for pharmacotherapy to be considered. Adult men must have a

minimum BMI of 30 kg/m2 or a waist circumference (WC) of 40 inches. Adult women must have

a minimum BMI of 27-30 kg/m2 or a WC of 35 inches. Additionally, these patients must have

completed six months of exercise, modified diet, and behavioral changes without successful

weight loss, and they must also have two risk factors as detailed above.17

Combined results from various clinical studies have reached the conclusion that Orlistat

increases weight loss and sustains weight loss maintenance, which will be discussed below.

Figure 1 summarizes weight loss results for particular Orlistat studies.

  7

Figure 1

A study by Torgerson et al. (2004) lasted four years and studied the efficacy of Orlistat.

The data showed there was more weight loss taking Orlistat for four years, compared to a

placebo. However, in order to maintain this weight loss, subjects had to continue taking the

medication, which could be considered a limitation of Orlistat. After one year, average weight

loss for the Orlistat group was 10.6 kg and after four years, average weight loss was 5.8 kg.

Another important component was that 72.8% lost at least 5% of their initial weight after one

year and 52.8% after four years. Additionally, losing weight via Orlistat decreased the risk of

developing type 2 DM by 37.3% when these subjects had decreased glucose tolerance. There

was improved regulation of blood sugar in type 2 DM subjects when Orlistat was used in

conjunction with a regulated diet. Other positive impacts of the Orlistat and diet combination

9.6%  

8.3%  

0  

5.3%   5.6%  

0  

6.6%  

0   0  

3.7%  

0  

3.7%  

5.1%  

0   0  

4.4%  

0   0  

5.9%  

0   0  

8.3%  

0   0  0.0%  

2.0%  

4.0%  

6.0%  

8.0%  

10.0%  

12.0%  

Weight  Loss  (kg)   WC  (cm)   BMI  (kg/m^2)    

Loss  (%

)  

Weight  Loss  Results  for  Selected  Orlistat  Studies  

Torgerson  et  al  |  Orlistat  120  mg  |  52  Weeks  

Torgerson  et  al  |  Orlistat  120  mg  |  208  Weeks  

Sumithran  et  al  |  Orlistat  60  mg  |  24  Weeks  

Douglas  et  al  |  Orlistat  (Unknown  Dosage)  |  16  Weeks  

Davidson  et  al  |  Orlistat  120  mg  |  104  Weeks  

Finer  et  al  |  Orlistat  120  mg  |  104  Weeks  

Krempf  et  al  |  Orlistat  120  mg  |  72  Weeks  

Rossner  et  al  |  Orlistat  120  mg  |  104  Weeks  

  8

include: decreased total and low-density lipoprotein (LDL) cholesterol, and enhanced regulation

of glucose levels.21

The efficacy of Orlistat is improved when there is a multi-component weight loss

regimen, as this helps with weight loss maintenance. These components include: exercise,

appetite suppressants, decreasing food intake, decreasing caloric intake, and modifying eating

behaviors. There is a natural weight gain once Orlistat is no longer administered, which is why

these various components are important in limiting this weight regain.17 Clinical trials also

reached the conclusion that by combining Orlistat and a decreased caloric diet, 10% body weight

can be lost in a year, showing the importance of multi-component diets.12

Dombrowski et al. (2014) reviewed long-term weight loss maintenance interventions in

obese adults with Orlistat. These studies selected obese adults who had an average BMI of at

least 30 kg/m2 and lost a minimum 5% body weight within two years before the Orlistat

treatment. Orlistat was used for weight loss maintenance for these subjects who had previously

lost weight on their own. Five studies observed the effects of taking Orlistat at 30, 60, or 120 mg,

three times daily. The results concluded that Orlistat, in combination with lifestyle changes,

caused an average 1.80 kg weight loss after 12 months. The optimal dosage for improved weight

loss maintenance was 120 mg, three times a day, which caused an average 2.34 kg weight loss.

In contrast, taking 30 or 60 mg, three times a day, caused an average 0.70 kg weight loss. This

meta-analysis concluded that Orlistat, in combination with lifestyle and behavior changes, is

effective for weight loss maintenance. Evidence pointed to Orlistat being effective over a span of

three years when taking the optimal dose of 120 mg, three times daily. Behavioral changes,

including diet and exercise, are somewhat effective for weight loss maintenance in obese adults

for up to two years, meaning weight regain is decreased. When supplementing these changes

  9

with Orlistat, there is some evidence showing that weight regain is decreased for up to three

years.6

Feigenbaum et al. (2005) evaluated the effects of Orlistat and weight loss follow-up in

three primary care offices. Primary care physicians can recommend nutritional changes,

exercises, and prescribe medication. Strictly using a diet and exercise plan is not effective in

terms of weight loss maintenance, since 95% of people regain the weight plus some within five

to seven years. Drug therapy used with a diet improves weight loss maintenance long-term.

Subjects were grouped into three treatments: A) personal diet, 120 mg Orlistat, and bimonthly

meetings with family physician and clinical dietitian; B) general diet, 120 mg Orlistat, and

monthly meetings with family physician for weigh-ins and prescription check-ups; C) low-

calorie personal diet, no medication, and monthly meetings with clinical dietitian. The daily

caloric intake was the same for the three groups: 1200 calories (women) and 1500 calories

(men). For Group A, the personal diet included foods the subject selected, while incorporating

low-fat options. The meetings included exercise recommendations and goals for diet with

positive reinforcement. The goal was to have 5% weight loss within six months and

improvement in their lipid panel. Results showed Group A had an average 5.12 kg weight

reduction, Group B had an average 7.8 kg weight reduction, and Group C had an average 3.12 kg

weight reduction. Group A had the most successful treatment had the most success in terms of

patients reaching their weight loss goal. 51% of subjects in Group A lost between five and ten

percent of their initial body weight. In all three groups, there was a decrease in triglycerides, and

Groups A and B had a significant decrease in low-density lipids (LDL), which are considered

“bad” cholesterol. In terms of high-density lipids (HDL), which are considered “good”

cholesterol, there was no change in any of the groups. The study concluded weight loss is

  10

successful in a primary care office with Orlistat. The fact that Group C had the lowest weight

reduction and did not include Orlistat in the plan shows its efficacy when used in a multi-

component diet plan.7

Sumithran et al. (2014) performed an analysis of Orlistat for weight loss maintenance and

noted various health parameters, including total weight loss, blood pressure, and cholesterol.

Orlistat causes an average 3 kg weight loss, waist circumference decrease of 2.1 cm, and BMI

decrease of 1.1 kg/m2. An average of 21% more subjects lost 5% of their initial weight and 12%

more subjects lost 10% of their initial weight, compared to a placebo. In terms of maintenance,

more subjects maintained their initial 5-10% weight loss after two years of taking Orlistat 120

mg compared to a placebo. Patients given a placebo for the first year post-treatment and then

Orlistat in the second year also maintained their initial weight loss. Comparatively, patients

receiving a placebo in the second year regained an average of 30-40% of their initial weight loss.

Orlistat can also be administered after a goal weight is achieved through other methods, such as a

diet. One study described in this review included patients who lost more than 8% of their initial

weight, then were given 30, 60, or 120 mg Orlistat or a placebo for one year. After one year,

those given 120 mg had less weight regain than the placebo, with a 32% weight regain taking

Orlistat and a 56% weight regain taking the placebo. 23.5% of Orlistat patients did not regain

weight or lost additional weight compared to 16.3% in the placebo group. Orlistat decreased

systolic blood pressure (SBP) by 1.9 mmHg and diastolic blood pressure (DBP) by 1.5 mmHg in

one study. SBP was decreased by 2.46 mmHg and DBP was decreased by 1.92 mmHg in another

study. Orlistat reduced total and LDL cholesterol levels more than with diet alone. For total

cholesterol, there was an average reduction of 0.27-0.38 mmol/L and for LDL, there was an

average reduction of 0.21-0.27 mmol/L. Another included study found that receiving Orlistat 120

  11

mg for six months reduced total cholesterol by 8.4% and LDL cholesterol by 10%. Orlistat

reduces LDL levels because it decreases cholesterol absorption. An additional study of

overweight adults with high cholesterol found that receiving Orlistat for six months, in

conjunction with a low-fat, low-calorie diet, decreased the levels of total cholesterol, LDL, and

triglycerides. It has been determined thus far that HDL levels are not effected by Orlistat. The

non-prescription form of Orlistat, Alli 60 mg, has about 80% efficacy, compared to the

prescription dose of 120 mg.19

Zohrabian et al. (2010) reviewed Orlistat in terms of clinical and economic

considerations. In general, weight loss from antiobesity medications is small, with values

typically from 2-10 kg. This weight loss is usually regained once the medication is stopped,

showing poor weight loss maintenance. Orlistat has the least side effects compared to other

antiobesity medications, but causes the least amount of weight loss, with an average of 3 kg.

After taking Orlistat for one year, regain of weight loss can occur even while taking the

medication. This study concludes that Orlistat is not significant for long-term health changes.

Even though it reduces diabetes risk and improves lipid panels and blood pressure values, these

are considered short-term benefits and most people do not continue taking Orlistat for long

periods of time.25

Sumithran et al. (2014) also reported some negative side effects while taking Orlistat,

even though it is considered a safe medication to take for extended periods of time. A negative

attribute of Orlistat is the possibility of an increase in appetite and desire for foods that increase

energy, which could cause weight regain. Other side effects occur in the gastrointestinal system

and include: fecal urgency, pain in the abdomen, incontinence, and fatty and oily feces due to

inhibition of lipase function. These side effects become worsened when there is an increase in fat

  12

intake in the diet, which is necessary for Orlistat to be effective. These side effects have been

found to lessen as treatment continues. After one year, 91% of patients reported at least one GI

issue, but after four years, this decreased to 36%. Orlistat can also decrease the absorption of fat-

soluble vitamins. Thus, Orlistat users should supplement their treatment with fat-soluble

vitamins. Some of the particular vitamins affected include vitamin A, D, E, and beta-carotene,

but taking a multivitamin usually helps with these reductions in vitamin levels.19

IV. B. Meal Replacement Products

Meal replacement products are an alternative method for losing weight and maintaining

this weight loss, and various studies, which will be further described below, support these claims.

These quick and easy products often include pre-made shakes, drinks, powders, bars, and

entrees, and products such as SlimFast and Herbalife are popular examples. Meal replacements

substitute regular meals with low calorie products.2 Most products are calorie-reduced and meant

to replace one or two meals or snacks per day with a low fat and low energy diet.8 A study from

Basciani et al. (2015) discusses how decreased efficacy in terms of weight loss maintenance can

be attributed to lack of compliance. People want quick weight loss without much work when in

reality, programs must be followed for an extended period of time. People become disheartened

when they have significant weight loss initially, but then plateau. This is where meal replacement

products come in handy, which are composed of the necessary nutrients to decrease fat tissue

size. Weight loss maintenance is also a critical component of any diet. A study by Vázquez et al.

(2009) describes how the benefits of weight loss last only as long as the weight loss is

maintained. Many people regain the weight because of hormones, adaptive physiological

changes, and not monitoring the weight loss maintenance. Weight loss maintenance can occur if

there is a low-fat and low-energy diet, exercise, self-regulation, and professional assistance.23

  13

Each kilogram lost decreases the risk of diabetes by 16%, and also decreases cardiovascular risk

factors.23 It has also been found that replacing one or two meals a day, which is called partial

meal replacement, increases subject compliance when compared to food plans.11 The following

studies will detail the benefits of using meal replacement products for weight loss and

maintenance. These benefits are evaluated in terms of total weight loss, decrease in BMI and

waist circumference, and various biomarkers, among other factors that will be further explained

below.

Studies that researched the efficacy of partial meal replacement diets looked at replacing

at least one daily meal with a meal replacement product, but still including regular healthy meals.

Partial meal replacement is a food-based strategy to decrease caloric intake. Moderately

decreasing caloric intake with a partial meal replacement diet is beneficial in decreasing body fat

and maintaining this weight loss. This treatment works slowly and progressively, which helps

with weight loss maintenance and a partial meal replacement diet is more flexible and convenient

than doing a total meal replacement diet.10 Partial meal replacements are said to be effective

because they provide reduced-calorie foods that take away the temptation to choose food that

may not be as healthy or nutritious. For the consumers, these products allow them to learn

portion control while having a normal lifestyle, and weight loss is more gradual. These products

are also easy to use and not as expensive.8 In terms of health content, meal replacement products

usually have at least 0.8 grams of protein/kg of ideal body weight each day in order to maintain

lean mass.2 Some of the meal replacement products used in these studies on overweight and

obese subjects were: Herbalife ShapeWorks, Optifast, SlimFast, Special K products, Modifast,

and Glucerna. Lee et al. (2009) accounted for the exercise regimens of the two groups for the

high protein and conventional diets and found that there was no significant difference between

  14

the two. Additionally, Heymsfield et al. (2003) gave all subjects the same exercise instructions to

supplement their diet plan.

These studies concluded that partial meal replacements were effective in overall mean

weight loss. There were also decreases in BMI, waist circumference, and fat mass. A decrease in

waist circumference is significant because this has been associated with decreased cardiovascular

risks.2 Table 1 outlines the averages of weight loss results for selected partial meal replacement

studies. In terms of biomarkers, levels of blood glucose, total cholesterol, serum triglycerides,

low-density lipoprotein (LDL), and insulin were decreased and high-density lipoprotein (HDL)

levels tended to increase. Li et al. (2005) also found a decrease in triacylglycerol levels.

However, the metabolic profile showed decreased glucose levels after six months compared to

the control group, but not after 12 months. The insulin levels were not different. Two studies by

Li et al. (2005) and Vander Wal et al. (2007) found small decreases in HDL levels, which was

different from other studies. Basciani et al. (2015) found that systolic and diastolic blood

pressure decreased. However, this study found a 5.2% increase in lean body mass, which could

be attributable to the protein requirement of 0.8 grams/kilogram of goal weight in the diet plan.2

Heymsfield et al. (2003) concluded that glucose, triglyceride, and systolic blood pressure levels

were considered significantly improved with weight loss after three months, as well as

improvement in risk factors for disease. After 12 months, total cholesterol, LDL, glucose,

triglyceride, and systolic blood pressure levels were all considered significantly improved.8

Vander Wal et al. (2007) found partial meal replacements were effective in decreasing hip and

thigh circumferences, but found that for cardiovascular risks, there were no significant

differences for glucose, lipids, and other biochemical levels and the results were not considered

significant enough for cardiovascular benefits.22 Table 2 outlines the averages of biomarker

  15

results for selected partial meal replacement studies. Figure 2 summarizes weight loss results for

particular partial meal replacement studies.

Vázquez et al. (2009) studied weight loss maintenance in particular, which is just as

important as initially losing weight. This study showed that a majority of the subjects maintained

their weight loss or lost additional weight in the maintenance phase. There was also a larger

decrease in absolute weight loss with the meal replacement group, however decreases in body fat

mass and fat free mass were similar for both groups. Additionally, this study found there were no

significant differences between the two groups in terms of waist circumference, fasting glucose,

lipid profiles, and blood pressure, but HDL levels increased.23

  16

Table 1 Averages of weight loss results for selected partial meal replacement studies

Study Body weight

(kg)

Waist Circumference

(cm)

BMI (kg/cm2)

Truncal Fat Mass

(kg)

Whole Body Fat Mass

(kg)

Lean Body

Mass (kg) Lee et al.

High Protein Diet 3 months

-5.0 -6.3 -1.9 -1.6 -2.5 -1.1

Lee et al. Conventional Diet

3 months

-4.9 -7.1 -1.8 -1.5 -2.3 -1.7

Basciani et al. 4-Stage Program

6 months

-14.7 -12.2 -5.2 x x x

Li et al. Soy-Based MR

12 months

-4.35 x -1.44 x x x

Heymsfield et al. Liquid MR 3 months

-6.19 to

-6.50

x x x x x

Heymsfield et al. Liquid MR 12 months

-6.97 to

-7.31

x x x x x

Vander Wal et al. Cereal/nutrient bar

1 month

-3.27 -6.05 -1.18 x x x

Vander Wal et al. Cereal/waffle/nutrient bar

1 month

-2.80 -5.23 -1.08 x x x

Vander Wal et al. Cereal/no nutrient bar

1 month

-3.45 -5.93 -1.30 x x x

  17

Table 2 Averages of biomarker results for selected partial meal replacement studies

Study Glucose (mg/dl)

Total Cholesterol

(mg/dl)

Triglycerides (mg/dl)

HDL (mg/dl)

LDL (mg/dl)

SBP (mmHg)

DBP (mmHg)

Lee et al. High Protein Diet

3 months

-3.8

-18.6

-70.1

+5.9

x

x

x

Lee et al. Conventional

Diet 3 months

-4.2

-11.1

-56.4

+7.6

x

x

x

Basciani et al. 4-Stage Program

6 months

-14.5

-15.2

-44.2

-0.1

x

-6.0

-6.2

Li et al. Soy-Based MR

12 months

-12.07

-10.76

x

-0.97

-6.10

x

x

Vander Wal et al. Cereal/bar 1 month

-3.6

-9.91

-3.78

-3.42

-4.86

x

x

Vander Wal et al. Cereal/waffle/bar

1 month

+1.62

-5.05

+0.36

-2.34

-2.88

x

x

Vander Wal et al. Cereal/no bar

1 month

-1.98

-9.37

-4.14

-3.60

-3.78

x

x

Figure 2

6.6%$ 6.6%$ 6.7%$6.4%$

7.4%$

6.3%$

15.4%$

12.1%$

15.4%$

4.6%$

0.0%$

4.4%$

7.3%$

0.0%$ 0.0%$

8.2%$

0.0%$ 0.0%$

3.3%$

0.0%$

3.2%$2.7%$

0.0%$

2.9%$

3.5%$

0.0%$

3.5%$

0.0%$

2.0%$

4.0%$

6.0%$

8.0%$

10.0%$

12.0%$

14.0%$

16.0%$

18.0%$

Body$weight$(kg)$ Waist$(cm)$ BMI$(kg/cm^2)$

Loss$(%

)$

Weight$Loss$Results$for$Selected$Par8al$Meal$Replacement$Studies$$

Lee$et$al$|$High$Protein$Diet$|$12$Weeks$

Lee$et$al$|$ConvenNonal$Diet$|$12$Weeks$

Basicani$et$al$|$4OStage$Program$|$24$Weeks$

Li$et$al$|$SlimFast$Soy$O$Based$MR$|$52$Weeks$

Heymsfield$et$al$|$PMR$Plan$|$12$Weeks$

Heymsfield$et$al$|$PMR$Plan$|$52$Weeks$

Vander$Wal$et$al$|$Special$K$Cereal$/$Nutrient$Bar$

|$4$Weeks$

Vander$Wal$et$al$|$Special$K$Cereal$/$Waffle$/$

Nutrient$Bar$|$4$Weeks$

Vander$Wal$et$al$|$Special$K$Cereal$/$No$Nutrient$

Bar$|$4$Weeks$

  18

The specific studies that concluded similar findings had their own variations of partial

meal replacement diets. Lee et al. (2009) researched the efficacy of a low-calorie and partial

meal replacement diet in obese subjects that had metabolic syndrome. The purpose of this study

was to research the effectiveness of high-protein versus conventional diets that both have partial

meal replacements. The meal replacement plan required that the subjects consume the meal

replacement products two times a day and a normal meal once a day. Overall, the high-protein

diet decreased body fat more than the conventional plan. This study suggests that a high-protein

diet with partial meal replacement could be useful for decreasing weight and abdominal in obese

subjects diagnosed with metabolic syndrome.10

Basciani et al. (2015) also researched a low-calorie and partial meal replacement diet by

evaluating a four-stage program that used meal replacement products and a very low calorie diet

(VLCD) at the start, while slowly adding more food into the diet to ultimately end up at a

hypocaloric balanced diet (HBD). The subjects slowly transitioned from four or five meal

replacement protein products in the first stage to a HBD with one meal replacement in the last

stage. The results showed a range of weight loss between 8.0 and 35.7 kg. Each month, there was

an average weight loss of 2.45 kg and overall, there was an average weight loss of 15.4%. This

program is unique because it included stages that slowly moved from a very low calorie diet to a

HBD. It was concluded that this multi-step program is a safe way to treat obesity and guide

people to a healthier lifestyle. Weight loss maintenance was best when transitioning from a

VLCD and slowly adding carbohydrates to a healthy level.2

Li et al. (2005) studied the effects of a soy-based meal replacement in obese subjects

diagnosed with type 2 diabetes. This plan progressed from three meal replacement shakes per

day, to two meal replacements and a regular meal, and lastly one or two meal replacements and

  19

one or two regular meals. The mean weight loss was 2.28% higher than the control group. The

study concluded that between the meal replacement and control groups, the levels for total

cholesterol, triacylglycerol, HDL, and LDL were not considered significantly different. A

significantly positive benefit of the meal replacement treatment was that many of the subjects

decreased their intake of metformin and sulfonylurea, which are medications used to manage

type 2 diabetes. Overall, this study concluded there was significant weight loss with a soy-based

meal replacement for type 2 diabetics.11

Heymsfield et al. (2003) published a meta and pooling analysis of weight management

with partial meal replacement, which was the first study until that point to perform an assessment

of the efficacy and safety of meal replacements. The study describes a partial meal replacement

plan as a low calorie diet containing one or two meal replacements with reduced calorie snacks

and meals. The subjects used liquid meal replacements twice a day in the weight loss phase and

one replacement a day in the maintenance phase. After three months, weight loss for the meal

replacement group was found to be an average 7% loss. After 12 months, weight loss was found

to be an average 7-8% loss. An important result was that after three months, 72% of meal

replacement subjects lost at least 5% of their initial body weight, and after 12 months, 74% lost

this amount of weight. The study concluded that a partial meal replacement plan causes more

weight loss and maintenance when compared to a control group, in this case a reduced calorie

diet. The average amount of weight loss for these subjects after 12 months is considered enough

to lower risk of disease. An interesting component was that the researchers compared diabetic to

non-diabetic subjects after 12 months and found that diabetics’ weight loss maintenance was

lower than nondiabetic subjects, which can be attributed to their use of insulin.8

Vander Wal et al. (2007) researched cereal partial meal replacements and the effects on

  20

weight loss, cardiovascular risks, and compliance. This study describes how low and moderate

carbohydrate diets are most effective in decreasing weight, fat, and waist/hip/thigh

circumferences. There were three types of meal replacement groups: cereal plus nutrient bar for a

snack, cereal and a waffle plus nutrient bar, and cereal with no nutrient bar. These groups were

able to choose a third meal of their own, so they had two replacement meals per day. The results

found that adherence to the three diets was high and all three had significant decreases in weight,

BMI, and hip, waist, and thigh circumferences, and body fat percentage for the cereal/nutrient

bar and cereal/no nutrient bar groups. For the cardiovascular risks, there were no significant

differences between the three groups for glucose, lipids, and other biochemical levels and the

results were not considered significant enough for cardiovascular benefits. There were also no

significant differences between the groups for urges to overeat, thinking about food more than

normal, craving food/hunger, and guilt for submitting to cravings, among other emotional

factors. This study concluded that adherence was better for the cereal/nutrient bar and cereal/no

nutrient bar plans, which could be explained by the fact that they required fewer products to

implement daily. Also, these products are helpful for short-term weight loss, since this was not a

long-term study and accounted for four-week changes.22

Vázquez et al. (2009) researched the efficacy of a meal replacement with a low caloric

intake formula that replaced dinner in regard to weight loss maintenance. This study gives a

guideline of how meal replacement products can be used to maintain weight loss after losing the

weight initially by dieting. The results showed that in the meal replacement group compared to a

control group, 83.9%, or 26 of the 31 subjects, maintained their weight loss or lost additional

weight and decreased their initial weight from the start of the maintenance phase by 3.2 kg.

There was also a larger decrease in absolute weight loss with the meal replacement group, which

  21

was 3.1 kg. It was concluded that using a meal replacement that is low-calorie is better for

weight loss maintenance when contrasted with dieting. The subjects had better weight loss

maintenance and lost over two times the weight without losing more lean body mass. The study

concedes that maintenance is difficult, but the benefits of using meal replacement formulas are

considered safe, easy to follow, and cost less than pharmaceutical drugs, with similar results.

There is also evidence that meal replacement products can be used to initially begin the weight

loss phase, while also maintaining it afterwards. The researchers believe that enhanced weight

loss maintenance and increased weight loss in the maintenance phase can occur if there is a more

gradual drop in weight during the induction stage.23

Ross et al. (2016) published a review article researching very low energy meal

replacements for weight loss in obese subjects who are about to undergo surgery. Even though

this study is focused on a group of people that are having surgery, it gives beneficial information

on meal replacements targeting weight loss since it studied short-term weight loss for an average

of four weeks. This very low energy diet contained decreased fat and carbohydrates and high

protein to maintain lean body mass while decreasing fat. In terms of percentage of total weight

loss, ten studies found subjects lost more than 5% of their starting weight, which as stated before,

causes various health benefits and decreases risk factors. Seven studies found subjects lost more

than 10% of their starting weight. Six studies also measured fatty liver size and its reductions

throughout the process and found liver reductions greater than 10%. Liver reduction is helped

when there is a change in diet and decreases in weight and BMI. There were also decreases in

total fat mass and thickness of adipose and visceral tissue. In follow-up measurements, it was

found that risk factors such as levels of insulin, glucose, and lipids were all improved. This study

shows that meal replacement plans are relatively easy to adhere to and can be used in clinical

  22

settings for interventions.15

An important component of any diet is how satisfied and “full” the consumer feels after

eating, which helps prevent overeating. Tieken et al. (2007) researched whether solid or liquid

meal replacements are more effective in regulating hunger and feeling full by affecting appetite-

regulating hormones. These appetite-regulating hormones include leptin, insulin, ghrelin, and

cholecystokinin (CCK), which regulate eating and body weight. When the subjects consumed the

solid and liquid products, it was found that after one hour, hunger in the solid group increased

less than the liquid group. After four hours, hunger in the solid group was 45% lower than

fasting level, but hunger in the liquid group was 14% higher than fasting level. The desire to eat,

over the span of four hours, was lower for the solid group compared to the liquid group. Blood

glucose levels increased significantly after 15 minutes with the liquid meal replacement, but took

60 minutes to increase significantly for the solid meal replacement. Insulin levels were lower

after 15 and 120 minutes for the solid group. Ghrelin levels were also lower in the solid group

and were lower than baseline levels up to four hours after eating. Leptin and CCK levels were

similar between the solid and liquid groups and hardly changed over the four-hour post-meal

period, however. Overall, it was concluded that solid meal replacements, such as a nutrient bar,

cause decreased hunger and desire to eat after consumption and are not equivalent to liquid meal

replacements for weight loss. These results are important because this can help people increase

and maintain their weight loss since it is easier to comply with a diet that makes you feel more

full and satisfied.20

IV. C. Medifast

The Medifast program is a paid weight loss and maintenance regime that works with

clients to reach their goals. Medifast is a type of meal replacement plan that has meals pre-made

  23

for clients that are proper portion sizes so they do not have to worry about cooking their meals

properly.18 There are two approaches for clients, which includes either following the program on

their own or going to Medifast Weight Control Centers. If a person chooses to follow the plan on

their own, they can find the right plan for them on the Medifast website. The options are either

the Flex Plan for gradual weight loss or the Go! Plan for rapid weight loss. The Flex Plan has

four Medifast meals, two Lean & Green meals (lean protein and vegetables), and one healthy

snack, making it the 4 & 2 & 1 Plan. The Go! Plan has five Medifast meals and one Lean &

Green meal, making it the 5 & 1 Plan. Once the client decides the plan that works for them, they

can order the meals online, which are then shipped to their home. There are options where clients

can order 30 days of meals or individual products. The other approach for clients at the Medifast

Weight Control Centers is more personalized and includes a body composition analysis and face-

to-face counseling.13 Medifast Weight Control Centers supervise clients to ensure they are

meeting their weight loss goals by having scheduled visits, ensuring they are following their

meal replacement plans, and encouraging them to keep a food/exercise diary. Medifast combines

Medifast meals and traditional food for a balanced diet plan. The Medifast program gathers

information about the client’s health before determining a suitable plan, including a health

review with their past medical history and blood work. Each client meets weekly with their

counselor, and the weekly sessions are comprised of: weigh-ins, blood pressure evaluation,

ketone testing, looking at their food diary, behavioral and lifestyle changes, and choosing meals

for the following week. Clients also have the option of measuring their body fat mass, lean

muscle mass, and percent body fat every four weeks, at an additional cost. The weight loss phase

length depends on each client, so no two plans are alike.3 The meal plans are customized to each

client’s individual needs and are based on the lifestyle of the client, their preferences, and past

  24

medical history. The client and counselor determine the weight loss goal, and then an

individualized weight loss phase and weight management program is created.4

The Medifast three-step approach is: active weight loss, transition, and maintenance. The

active weight loss phase uses one of the Medifast plans, such as the 5 & 1 Plan described above.

The transition phase has the clients slowly decrease the number of Medifast meals and add

traditional food that gives them their energy needs to maintain their weight loss. The length of

the transition phase depends on how much weight was lost: 50 pounds is an eight week phase,

51-100 pounds is a 12 week phase, and greater than 100 pounds is a 16 week phase. The

maintenance phase lasts 52 weeks and includes a set meal plan with Medifast meals and

traditional foods. This meal plan is also individualized and is determined by the energy needs

necessary for long-term weight loss maintenance.3

The studies below included overweight and obese subjects and concluded that the

Medifast program is effective for not only weight loss, but also maintenance. An additional

benefit of this program is the improvement of various biomarkers that decrease the risk for

various diseases, particularly cardiovascular disease. Table 3 summarizes the averages of weight

loss results and Table 4 summarizes the averages of the biomarker results. Figure 3 summarizes

weight loss results for particular Medifast studies.

  25

Table 3 Averages of weight loss results for Medifast studies Study Body

Weight (kg)

Waist Circumference

(cm)

BMI (kg/cm2)

Fat Mass (kg)

Fat-free Mass (kg)

Lean Muscle Mass (kg)

Shikany et al. 5 & 1 Plan Weight loss (26 weeks)

-7.5

-5.7

-2.6

-6.4

-1.2

x

Shikany et al. 5 & 1 Plan

Maintenance (52 weeks)

-4.7

-5.0

-1.6

-4.1

-0.6

x

Davis et al. 5 & 1 Plan Weight loss (16 weeks)

-13.5

-13.0

-4.7

x

x

-1.8

Davis et al. 5 & 1 Plan

Maintenance (40 weeks)

-8.9

-9.7

-2.9

x

x

-1.8

Coleman et al. 4 & 2 & 1 Plan

12 weeks

-10.9

-9.8

-3.7

x

x

x

Coleman et al. 4 & 2 & 1 Plan

24 weeks

-16.0

-13.6

-5.5

-14.5

x

-3.1 Coleman et al.

5 & 1 Plan 4 weeks

-5.8

-4.1

x

-4.6

x

-1.9

Coleman et al. 5 & 1 Plan 12 weeks

-11.9

-10.2

x

-9.2

x

-2.0

Coleman et al. 5 & 1 Plan 24 weeks

-17.3

-15.2

x

-14.3

x

-2.8

  26

Table 4 Averages of biomarker results for Medifast studies Study SBP

(mmHg) DBP

(mmHg) Total

Cholesterol (mg/dl)

Triglycerides (mg/dl)

HDL (mg/dl)

LDL (mg/dl)`

HR/Pulse (bpm)

Glucose (mg/dl)

Shikany et al. 5 & 1 Plan Weight loss (26 weeks)

-3.2

-1.6

-8.4

-3.7

+1.2

-9.2

x

-1.1

Shikany et al. 5 & 1 Plan

Maintenance (52 weeks)

-0.5

+0.6

-0.3

-7.5

+2.1

-1.3

x

-2.2

Davis et al. 5 & 1 Plan Weight loss (16 weeks)

-10.9

-6.5

-9.9

-17.4

-0.4

-5.9

-9.2

x

Davis et al. 5 & 1 Plan

Maintenance (40 weeks)

-6.0

-5.5

-9.2

-1.5

+1.2

-10.2

-6.6

x

Coleman et al. 4 & 2 & 1 Plan

12 weeks

-11.3

-6.6

x

x

x

x

-3.0

x

Coleman et al. 4 & 2 & 1 Plan

24 weeks

x

x

x

x

x

x

-3.7

x

Coleman et al. 5 & 1 Plan

4 weeks

-8.0

-5.3

x

x

x

x

-2.8

x

Coleman et al. 5 & 1 Plan 12 weeks

-8.6

-6.4

x

x

x

x

-4.1

x

Coleman et al. 5 & 1 Plan 24 weeks

-15.6

-9.2

x

x

x

x

-3.7

x

  27

Figure 3

The specific studies researched the Medifast program, but with their own approaches.

Shikany et al. (2013) researched the Medifast 5 & 1 Plan, which includes portion-controlled, low

fat, and nutritional meals. This study compared the Medifast diet to a reduced-energy diet with

meals selected by the subject based on healthy food lists. The Medifast 5 & 1 Plan is available

for purchase and the program setup is five meals and a meal the client chooses with lean protein

and three vegetable servings every day. The Medifast group during the weight loss phase was

provided five low-fat meals and the choice of one “Lean & Green” meal, which was lean protein

and vegetables. The subjects had the choice between 70 meals for their five meals a day and

consumed 800-1000 kilocalories daily. The “Lean & Green” meal consisted of five to seven

ounces of lean meat or other protein, 0-2 servings of healthy fat, and three 0.5-1.0 cup servings

of vegetables that were low in carbohydrates. Subjects also become part of an online community,

where they could talk with trainers and dietitians and chat with other people in the program.

Recipes were also provided. For both groups during the weight loss maintenance phase, the

subjects’ energy needs were calculated to maintain their weight while also factoring in their daily

6.7%%

5.3%%

6.4%%

4.2%%4.6%%

4.0%%

12.1%%

11.1%%

12.2%%

8.0%%8.3%%

7.5%%

10.0%%

0.0%%

9.9%%

14.7%%

0.0%%

14.7%%

6.0%%5.5%%

0.0%%

12.1%%

8.5%%

0.0%%

17.0%%

12.4%%

0.0%%

0.0%%

2.0%%

4.0%%

6.0%%

8.0%%

10.0%%

12.0%%

14.0%%

16.0%%

18.0%%

Body%Weight%(kg)% Waist%Circumference%(cm)% BMI%(kg/m^2)%

Loss$(%

)$

Weight$Loss$Results$for$Selected$Medifast$Studies$$

Shikany%et%al.%|%5%&%1%Plan%|%Weight%Loss%|%26%weeks%

Shikany%et%al.%|%5%&%1%Plan%|%Maintenance%|%52%weeks%

Davis%et%al.%|%5%&%1%Plan%|%Weight%Loss%|%16%weeks%

Davis%et%al.%|%5%&%1%Plan%|%Maintenance%|%40%weeks%

Coleman%et%al.%|%4%&%2%&%1%Plan%|%12%weeks%

Coleman%et%al.%|%4%&%2%&%1%Plan%|%24%weeks%

Coleman%et%al.%|%5%&%1%Plan%|%4%weeks%

Coleman%et%al.%|%5%&%1%Plan%|%12%weeks%

Coleman%et%al.%|%5%&%1%Plan%|%24%weeks%

  28

total energy expenditure. For the Medifast subjects, they were able to have 0-3 meals for their

individual calculated energy needs, and the other group made their own meals. Overall, the

Medifast group decreased their weight, BMI, waist circumference, and fat mass from the starting

weight. This study concluded that Medifast yielded better results for weight, BMI, waist

circumference, and fat mass after 26 weeks compared to the reduced-energy diet, which was the

weight loss phase. The Medifast plan also maintained their weight, BMI, and fat mass after 52

weeks, which was the maintenance phase. Compared to the other diet, decreases in cholesterol

and LDL were greater in the Medifast group after 26 weeks. At the 52-week mark, there were

greater decreases in weight, BMI and fat mass in the Medifast group. The authors discussed how

portion control helps with weight loss because people do not have to make the portion sizes on

their own, with the possibility of making them too large. A plan that is set and organized makes

it easier to follow, and in this study, more people finished the Medifast diet compared to the

other diet. The strength of this study is that the Medifast plan incorporates real food, which the

authors think is a more realistic way to lose weight and incorporate into a regular diet plan.18

Davis et al. (2010) compared two hypocaloric diets: Medifast 5 & 1 Plan and an

isocaloric food diet, and both were comprised of 1000 kilocalories daily. The maintenance phase

included a slow increase of calories so the subjects’ energy levels could be maintained with three

to five Medifast meals. The results showed that in the weight loss phase, 92.9% of Medifast

subjects lost at least 5% of their initial body weight, whereas 55% of the isocaloric diet subjects

did so. Additionally, 75% of Medifast subjects lost at least 10% of their initial body weight,

whereas 25% of the isocaloric diet subjects did so. For the maintenance phase, 61.5% of

Medifast subjects maintained at least 5% weight loss and 30% of the isocaloric diet subjects did

so. Additionally, 38.5% of Medifast subjects maintained at least 10% of their weight loss and

  29

20% of isocaloric diet subjects did so. There were significant improvements only in the Medifast

group for DBP and waist circumference after 40 weeks. Decreases in central obesity and waist

circumference also decrease the risks for coronary heart disease and mortality, among other risk

factors. The study concluded that the Medifast diet had twice the weight loss compared to other

diet during the 16-week weight loss period. Even though the Medifast group had more weight

regain during the maintenance period, the Medifast group was better at maintaining clinically

significant weight loss (which is 5% of initial weight within a year). The Medifast group lost

more body fat and visceral fat and maintained their lean muscle mass. Maintaining lean muscle

mass is important for overall weight loss maintenance. The low fat, low carbohydrate, and high

protein diet of Medifast can account for this lean muscle mass maintenance.5 Lean mass helps

with the strength and physicality of subjects, and with their basal metabolic rate, which plays a

role in weight loss maintenance. It is suggested that 1.1-1.6 g/kg of body weight is consumed as

protein to maintain lean mass while losing body weight. The Medifast plan allows subjects to

consume adequate amounts of protein.4

Coleman et al. (2015) was a retrospective chart review study that evaluated the

effectiveness of Medifast in an actual setting, instead of a controlled study. The meal plan in this

study is the Medifast 4 & 2 & 1 Plan, which is greater in caloric intake compared to the typically

used Medifast 5 & 1 Plan. This higher-calorie plan can be used for clients who exercise

frequently or wish to consume dairy, grains, and fruit every day, which is usually not allowed in

other types of weight loss programs. The Medifast 4 & 2 & 1 Plan is 1,100-1,300 kilocalories per

day. The plan includes: four Medifast meals, two lean protein and vegetable meals, and one

snack, which can consist of grains, dairy, or fruit. The Medifast meals are comprised of 11-15

grams of protein, 8-15 grams of carbohydrates, and 0-3.5 grams of fat. The program has an

  30

optional transition phase where the amount of calories and traditional food is slowly increased to

mimic daily choices the clients will have to make. The maintenance phase is comprised of three

Medifast meals and three traditional meals the client makes, and the specific plan is formatted

based on their total energy expenditure. Weight loss was considered significant after 24 weeks,

and the highest amount of weight loss occurred within the first two weeks of starting the

Medifast program. After 12 weeks, 85% of clients had decreased their initial weight by a

minimum 5%, and 50% of clients had decreased their initial body weight by at least 10%. After

24 weeks, 96% of clients had decreased their initial weight by at least 5% and 75% of clients had

decreased their initial weight by a minimum 10%. After four months, 50.2% of the clients who

completed the program lost a minimum 5% of their initial body weight. The first four weeks

showed decreases for SBP, DBP, and HR, which decrease the risk for cardiovascular disease.

This study was unique because it analyzed the differences in weight loss between males and

females. Males decreased their weight by 1.4 kg more than females over the span of 12 weeks.

Males decreased their body fat mass by 36.8% and females by 26.4%, and males lost more fat

mass than females. There were 14% of clients who went into the transition phase and lost an

additional 0.5 kg. Additionally, there were 20% of clients who went into the maintenance phase,

averaging 34 weeks long, and the average weight regain was 1.6 kg. At the end of the

maintenance phase, the average weight loss was 16.8 kg, which was 15-16% loss from the initial

starting weight. The clients who went through the Medifast maintenance phase decreased their

weight by 16.2 kg, whereas those who did not decreased their weight by 9.2 kg. Regardless of

the length of their individual plan, 70% of the clients decreased their weight by at least 5%. The

clients averaged one year on this Medifast program, and the average weight loss maintained was

17 kg, which concludes that Medifast is effective in terms of weight loss maintenance.4

  31

Coleman et al. (2012) also researched the Medifast 5 & 1 Plan. The average amount of

time for the weight loss phase was 19.6 weeks, the average time for transition was 7.9 weeks,

and the average time for maintenance was 16.3 weeks. The results showed that during the

transition phase, the average regain was 0.45 kg, but weight loss was still maintained from initial

weight, which was 15.4 kg. During the maintenance phase, the average regain was 1.9 kg, but

weight loss was still maintained from initial weight, which was 14.3 kg. The study found that

there was clinically significant weight loss of at least 5% with every client. At 24 weeks, the

average weight loss was 17.2 kg and clients maintained 97.5% of the weight they lost after the

maintenance phase. Medifast emphasizes body fat loss, and after 24 weeks, there was 8.5% loss

of body fat and 14.3 kg lost in fat tissue. The study concluded that Medifast is effective because

it keeps clients accountable with weekly individual sessions. It was found that clients who were

diligent with their weekly meetings lost more weight after six months compared to those who

were not as diligent.3

IV. D. Bariatric Surgery

Bariatric surgery has become an increasingly popular method for weight loss and its

efficacy is supported by results of clinically significant weight loss. There are about 344,000

bariatric surgeries each year around the world and there has been a significant increase in

laparoscopic bariatric surgeries over the years.17 The history of this surgery began in the 1950s

when it was known that people with a gastrectomy or short bowel syndrome had weight loss

because parts of their intestines were removed.9 Nowadays, this surgery alters the gastrointestinal

organs so body weight is lost through metabolic and physiological ways. Bariatric surgery is

effective through one of two methods: 1) decreasing consumption of food due to decreased

stomach size or 2) decreasing the absorption surface of the digestive tract, causing

  32

malabsorption. These surgeries decrease the feeling of hunger, alter food choices, enhance the

feeling of satiation when eating to prevent overeating, and altering energy use. There are various

types of bariatric surgery, which include gastric bypass, vertical sleeve gastrectomy, and

adjustable gastric banding.14

Bariatric surgery tends to be an option for people who have been unable to lose a

significant amount of weight by other means, such as diet, exercise, and pharmacotherapy. The

criteria for bariatric surgery are a BMI greater than 40 kg/m2 or a BMI of 35-40 kg/m2 and other

comorbid diseases, as well as ineffectual medical therapy. Recently, there has been approval for

people with BMI of 30-35 kg/m2 and type 2 diabetes. Additionally, if people are undergoing

bariatric surgery, they are counseled on obesity and that they must decrease their energy intake

after surgery. Their surgical risk is determined, such as if they have cardiovascular and

pulmonary diseases. If a patient had cardiovascular disease, it may be considered too high of a

risk to perform surgery. Assessment of the psychological state of patients can identify whether

they have depression, binge eating disorder, and other diseases that could impact the success of

the surgery.24

Some of the more common types of bariatric surgery will be described below. One type

of bariatric surgery is Roux-en-Y gastric bypass (RYGB). In this procedure, the stomach is

separated into two parts: the upper stomach pouch and lower, gastric remnant. The stomach

pouch is connected to the mid-jejunum via an anastomosis and the bowel continuity is restored.

The lower gastric remnant is closed off from food exposure. Another type of surgery is

adjustable gastric banding (AGB), where an adjustable plastic, silicone ring is placed around the

proximal part of the stomach, making a pouch. A third common procedure is the biliopancreatic

diversion, which includes a partial gastrectomy with a gastric pouch. The small bowel is also

  33

divided and a gastroenterostomy is made. One of the more popular procedures is the vertical

sleeve gastrectomy (VSG), which removes part of the lateral stomach and includes a

biliopancreatic diversion.14 Bariatric surgery has shifted to a more laparoscopic approach for

many of the procedures, which makes the surgery as minimally invasive as possible.24 The

mortality rate post-surgery has been reduced to 0.3%, making it a reasonably safe surgery,

despite the dramatic changes to the gastrointestinal system.14

Studies show that RYGB, AGB, and VSG bariatric surgical techniques can cause 20-35%

of total body weight loss, as well as weight loss maintenance. There are numerous health benefits

that are associated with this weight loss, including improvement in cardiovascular, respiratory,

renal, metabolic, and musculoskeletal diseases, and a decrease in mortality rates.14 Figure 4

summarizes weight loss results for particular bariatric surgery studies.

  34

Figure 4

Miras et al. (2013) published a review on various types of bariatric surgery and their

effectiveness in not only weight loss, but also weight loss maintenance. This review discussed

how low-calorie diets are effective in the weight loss phase, but weight loss maintenance is

difficult because of behavioral patterns such as increased hunger and desire for food high in fats

and sugar. On the other hand, bariatric surgery has been found to change these behavioral

patterns so weight loss maintenance is achievable. Bariatric surgery allows people to decrease

hunger and increases satiation while eating so they feel full faster and do not overeat. In terms of

the food preferences of people who have undergone bariatric surgery, it has been found that

RYGB surgery causes patients to choose low-fat and low-sugar foods. An explanation for this

phenomenon includes avoidance and learning via physiological processes. Food preferences after

this type of surgery are affected by Dumping Syndrome, which causes abdominal pain and

nausea when a person consumes high-carbohydrate and high-fat foods. In terms of energy

16.10%&

42.60%&

50.30%&

55.20%&

77.50%&

55%&53.30%&

59.30%&63.20%& 63%&

70%&

84%&

79%&

13%&

25%&

16%&

44.30%&

61.10%&

12%&

45%&

15.90%&

0.00%&

10.00%&

20.00%&

30.00%&

40.00%&

50.00%&

60.00%&

70.00%&

80.00%&

90.00%&

Loss$(%)$

(1)$=$Ionut$et$al$(2)$=$Shah$et$al$$$(3)$=$Wolfe$et$al$

Weight$Loss$Results$for$Selected$Baria>c$Surgery$Studies$

(1)&10&year&avg.&&

(1)&LABG&&1&year&

(1)&LABG&&&2&years&&

(1)&LABG&&3&years+&

(1)&SG&&3&years&&

(1)&SG&&5&years&&

(1)&SG&&6&years&&

(1)&RYGB&&<2&years&

(1)&RYGB&>2&years&&

(1)&RYGB&&3&years&&

(1)&BPD&&Average&&

(1)&BPD&&3&years&&

(1)&Gastric&banding&&1&year&&

(1)&Gastric&banding&&10&years&&

(1)&Gastric&bypass&&10&years&&

(1)&VBG&&10&years&&

(2)&LSG&&1&year&&

(2)&LRYGB&&1&year&&Weight$Loss$(kg)$

  35

expenditure after bariatric surgery, it has been found that resting energy expenditure is stable or

decreased.14

Ionut et al. (2013) discussed how bariatric surgery has the highest efficacy for treating

obesity. After ten years, the amount of weight loss was 16.1%, which is significant. A few of the

procedures discussed include laparoscopic adjustable gastric banding (LABG), which is the most

common procedure. A silicone band is put around the stomach, which decreases the gastric size

and creates a pouch that is 15 ml in size. The size of the silicone band can be adjusted as

necessary, so the band can be tightened to increase weight loss. LAGB increases weight loss by

restricting the amount of food the person will ingest because of the reduction in gastric size.

Results show that the average weight loss is 42.6% after one year, 50.3% after two years, and

55.2% greater than three years. Additionally, there was an average weight loss of 27 kg less than

two years after surgery, and 38 kg greater than two years after surgery for LAGB. A sleeve

gastrectomy (SG) involves a left partial gastrectomy that makes the stomach a tubular shape,

with the size and shape resembling a banana. This physical change causes increased gastric

emptying, which means there is faster deposition of nutrients into the small intestine. The

average weight loss is 77.5% after three years and 53.3% after six years.9

The most common gastric bypass (GB) procedure is Roux-en-Y-gastric bypass (RYGB),

which is performed laparoscopically. This procedure decreases the gastric volume with a gastric

pouch that is 15-30 ml in size. The flow of nutrients is switched from the stomach to the

proximal jejunum, via an anastomosis. This causes a decrease in stomach size, faster gastric

emptying, as well as neural and hormonal differences. The average weight loss is 59.3% (45.3

kg) less than two years after surgery and 63.2% (41.4 kg) greater than two years after surgery.

The biliopancreatic diversion (BPD) procedure involves a gastrectomy and enteroenterostomy.

  36

This creates a bypass of the duodenum and entry for pancreatic and biliary secretions, which

causes slower food mixing with biliopancreatic secretions. Weight loss for this procedure is

70.0%, which is typically maintained long-term. Less than two years after surgery, there is

weight loss of 38.0 kg and greater than two years after surgery, weight loss averages 49.8 kg.

However, this procedure is used only 2% of the time around the world because there is evidence

of deficiencies in nutrients for patients. Comparatively, LAGB is the most common procedure,

indicating its safety and efficacy.9

Malabsorption is considered one way that such significant weight loss is achieved. Some

of these procedures, such as BPD and RYGB, bypass a large part of the small intestine so there is

no contact with the nutrients from ingested food. Another reason proposed for this dramatic

weight loss is a decrease in caloric intake after surgery, which is decreased to a very low amount,

typically 200-300 kcal daily. However, this is only immediately after surgery and is the cause for

weight loss initially. More long-term effects include a decrease in the length of time needed to

lose weight after bariatric surgery, compared to a low calorie diet. For example, people with

gastric bypass surgery lost 10 kg in 30 days, compared to 55 days for people on a low calorie

diet.9

Ionut et al. (2013) discusses the success of initial weight loss after bariatric surgery, but

the long-term weight loss maintenance efficacy was questioned. After ten years, the average

weight loss was 16%, specifically 25% in gastric bypass, 16% in VBG, and 13% in gastric

banding groups. It was found that 20% of people regained the weight after one to three years.

With gastric banding, there was 79% weight loss after one year, but BMI gradually increased by

0.42 kg/ m2 each year. With RYGB surgery, 56% of people regained their weight lost, and after

five years, weight regain was 84.8%. However, after three years, the weight loss was 63% for the

  37

RYGB group and 84% for the BPD group, specifically the duodenal switch surgery. Weight loss

success measures weight loss as greater than 50%, which was accomplished by 83% of people in

the RYGB group and 98% in the BPD duodenal switch group. For the SG procedure, there was a

55% weight loss after five years, while 19% of people regained at least 10 kg. There is no

specific reason for weight regain post-surgery, but some of the mechanisms proposed include

Peptide YY (PYY), leptin, and ghrelin. In rat models that had RYGB performed, weight loss was

not sustained in the rats that had low PYY to leptin concentration ratios. It was found in another

study that the amount of ghrelin was higher in patients who could not maintain their weight loss.9

Shah et al. (2016) compared weight loss in morbidly obese subjects after laparoscopic

vertical sleeve gastrectomy (LSG), which has become the more common procedure, compared to

laparoscopic Roux-en-Y gastric bypass (LRYGB). One of the reasons for this shift in popularity

of LSG is the American Society for Metabolic and Bariatric Surgery stated that sleeve

gastrectomy is now classified as a primary bariatric surgery. Additionally, there are fewer

complications after LSG than LRYGB. This study compared postoperative factors between the

groups after ninety days and found that the hospital stay length, admission to ICU, and

complications were similar for both procedures. However, the LRYGB group had more frequent

visits to the emergency department in this ninety-day period. After one year, the estimated body

weight loss for the LSG group was 44.3%, compared to 61.1% in the LRYGB group. Overall,

LRYGB was found to have greater weight loss one year after surgery, and other factors,

including a lower BMI and a lack of type 2 diabetes, also increased weight loss in this one-year

period. Type 2 diabetes can impact weight loss, and the possible mechanism for this is that the

medications people take for diabetes increase insulin in the blood, which causes lipogenesis.

These two procedures had similar rates of mortality and morbidity, however patients undergoing

  38

LSG had a lower risk of being hospitalized or going to the emergency department after surgery.

This study discussed how other studies found similar weight loss results comparing LSG and

LRYGB.16

Wolfe et al. (2016) researched the efficacy of bariatric surgery on not only weight loss,

but also other diseases caused by obesity. Weight loss is correlated with decreased risk of

comorbidities and a better chance of living a longer, healthier life. People with respiratory

failure, congestive heart failure, and difficulty moving around can improve these issues with

dramatic weight loss via bariatric surgery. Some comorbidities caused by obesity include:

cardiovascular, metabolic, pulmonary, musculoskeletal, and numerous other diseases that are

aimed to be improved with surgery. This study discusses the RYGB, sleeve gastrectomy,

biliopancreatic diversion, and adjustable gastric banding procedures. After the RYGB procedure,

there was 12% total body weight loss after six months and 45% after three years. Another report

included in this study showed weight loss during the three years after RYGB to be 30-35% total

body weight loss. With this procedure, there is some weight regain until three to five years after

surgery, but then typically plateaus at 30% total body weight loss, showing weight loss

maintenance for at least 10-20 years. For the LAGB procedure, weight loss averaged 15.9% after

three years. Bariatric surgery has been found to decrease triglyceride and LDL levels while

increasing HDL levels. One notable example is three years after RYGB surgery, dyslipidemia

was decreased in 62% of the patients. For patients with type 2 DM, a study compared RYGB or

BPD surgeries with medical interventions. A person is considered in remission from diabetes if

their HbA1c level is less than or equal to 6.5% and fasting plasma glucose level is less than or

equal to 5.6 mmol/L after two years, with no pharmacotherapy within the last year. Results

showed that 50% of patients were in remission after five years if they underwent surgery. In

  39

contrast, zero patients who underwent medical intervention were in remission after five years.

The benefits of weight loss from bariatric surgery include: decrease in visceral adipose tissue as

well as improved dyslipidemia, hypertension, diabetes, nonalcoholic fatty liver disease,

endothelial function, and obstructive sleep apnea.24

V. Discussion

  Obesity is a pervasive issue in the United States that needs resolution. This chronic issue

is often associated with various comorbid diseases that can often be improved with weight loss.

Oftentimes, weight loss does not have to be significant, and 5-10% of weight loss can

significantly improve a person’s quality of life. After considering the results of the four diet

methods selected, bariatric surgery is the most effective option for weight loss and maintenance,

which was hypothesized from the beginning. However, bariatric surgery is not available to

everyone based on their BMI and is used as a last option after all other weight loss methods have

been exhausted. Additionally, bariatric surgery is a dramatic life change and most people would

rather use other methods without putting themselves at risk for complications. A more suitable

diet plan is the Medifast program, which provides pre-made meals with the necessary nutrients

for steady weight loss. Additionally, there is the option of the Medifast Weight Control Centers,

where clients can have supervision and guidance during the process. This provides weekly one-

on-one sessions with a counselor and keeps clients accountable throughout the entire process

because they are being weighed and their progress is tracked. They are also receiving lifestyle

changes to make their weight loss life-long instead of temporary. This could keep someone

accountable and decrease the temptation of deviating from the plan. Additionally, the meal plan

is chosen that best suit the client’s lifestyle and diet wishes, making it personalized to them.

  40

Unfortunately, this program can become quite expensive if the client stays in the program for an

extended period of time, such as 52 weeks, which occurred in some of these studies.

By looking at each of the diet methods individually, it can be seen that they each have

their strengths and weaknesses. Orlistat, which is the pharmacological approach to weight loss,

has been shown to cause modest weight loss, and does not necessitate a dramatic life change in

order to use it. However, there are a few downsides. These include the fact that weight regain is

common once the medication is stopped. Additionally, the medication needs a diet with a higher

fat content to be effective because of its function as a lipase inhibitor. Once the medication was

discontinued, a high fat diet would need to be decreased because the body would no longer have

the lipase inhibitor. This may be difficult for some people to make this transition. Lastly, there

are side effects including fatty and oily stools due to the fat excretion, which people may find

unpleasant, but it should be noted that these side effects tend to decrease with time.

Partial meal replacement plans are the most common type of meal replacement plan

because this allows people to still maintain a more normal lifestyle. They are still able to choose

at least one regular, healthy meal per day, while they are learning lifestyle changes from the

portion controlled meal replacements. This allows people to slowly wean themselves off the

meal replacements or decrease the number of meals they are replacing because they are learning

new food habits that can be transitioned to regular food choices. These studies showed that meal

replacements increased weight loss and decreased BMI, fat mass, waist circumference, blood

pressure, and levels of insulin, glucose, triglycerides, LDL, and total cholesterol. HDL levels

increased in some studies but not all. The protocol that seemed to work best for a partial meal

replacement plan is the one detailed in Basciani et al. (2015), which was a four-stage program

using meal replacement products and a very low calorie diet (VLCD) at the beginning, while

  41

slowly adding more food to end up at a hypocaloric balanced diet (HBD). The subjects

transitioned from four or five meal replacement products in the first stage to one meal

replacement in the last stage. This allowed steady monthly weight loss with an average total

weight loss of 14.7 kg, which is a significant amount. This program allows the body to slowly

adapt to the new changes, and the hypocaloric balanced diet is feasible enough to continue into

the maintenance phase and long-term. An added benefit is that meal replacements can also cause

additional weight loss during the maintenance phase. All of these results are best coupled with

exercise throughout the weight loss intervention program and compliance with the meal

replacement plans.

Medifast, as discussed above, is effective for both weight loss and weight loss

maintenance. The limitation of the studies selected for this review are they follow the weight loss

of the subjects during the Medifast program, but not afterwards when they discontinue the

program. However, the Maintenance phase of the program sets the clients up for the future where

they are not completely dependent on Medifast meals and instills healthy habits. Programs such

as Medifast are popular weight loss options because people have the option of not doing the

work on their own through the Medifast Weight Control Centers. One of the most difficult parts

of any diet is choosing the correct foods that provide the healthy amount of nutrients, while also

maintaining the correct portion sizes. Medifast provides pre-made meals that are portion-

controlled and formulated with a healthy amount of vitamins, minerals, low fat, and protein. The

results showed not only weight loss, but also little weight regain in the maintenance phase.

Additionally, various biomarker levels were decreased to a healthier level, which decreases the

risk of disease for clients.

  42

Bariatric surgery is a reasonable option for people who have tried other weight loss

methods without success. When people are at the point of considering bariatric surgery, it usually

means they are morbidly obese and have tried diets, exercise, pharmacotherapy, and other

medical interventions. With this type of surgery, patients undergo extensive preoperative

assessments to ensure they are not only physically capable of this surgery, but mentally as well.

This surgery causes weight loss by physiologically changing the way the body digests and

absorbs food, as well as causing behavioral changes such as eating less because of a decrease in

appetite and feeling “full” more quickly. Though this surgery is an extensive lifestyle change, the

various types of bariatric surgery have been developed over the past few decades to minimize

surgical complications and can literally save the patient’s life by not only losing weight, but also

improving various comorbid diseases, including type 2 DM and dyslipidemia. It is important to

stress to these patients that they must also change their diet and they must know that they have to

implement lifestyle changes after this surgery. There will be some natural behavioral changes,

including the desire to eat less as noted above, but consciously eating healthy and exercising will

enhance the weight loss effects and ensure this weight loss is long-term.

   

   

  43

REFERENCES

1About Adult BMI. Retrieved from https://www.cdc.gov/healthyweight/assessing/bmi/adult_bmi/  2Basciani, S., Costantini, D., Contini, S., Persichetti, A., Watanabe, M., Mariani, S., . . . Gnessi, L. (2015). Safety and efficacy of a multiphase dietetic protocol with meal replacements including a step with very low calorie diet. Endocrine, 48(3), 863-870. doi:10.1007/s12020-014-0355-2 3Coleman, C., Kiel, J., Hanlon-Mitola, A., Sonzone, C., Fuller, N., and Davis, L. (2012). Use of the Medifast Meal Replacement Program for Weight Loss in Overweight and Obese Clients: A Retrospective Chart Review of Three Medifast Weight Control Centers (MWCC). Food and Nutrition Sciences, 3(10), 1433-1444. doi: 10.4236/fns.2012.310187. 4Coleman, C., Kiel, J., Mitola, A., Langford, J., Davis, K., & Arterburn, L. (2015). Effectiveness of a medifast meal replacement program on weight, body composition and cardiometabolic risk factors in overweight and obese adults: A multicenter systematic retrospective chart review study. Nutrition Journal, 14(1), 77. doi:10.1186/s12937-015-0062-8 5Davis, L. M., Coleman, C., Kiel, J., Rampolla, J., Hutchisen, T., Ford, L., . . . Hanlon-Mitola, A. (2010). Efficacy of a meal replacement diet plan compared to a food-based diet plan after a period of weight loss and weight maintenance: A randomized controlled trial. Nutrition Journal, 9(1), 11-11. doi:10.1186/1475-2891-9-11 6Dombrowski, S. U., Knittle, K., Avenell, A., Araújo-Soares, V., & Sniehotta, F. F. (2014). Long term maintenance of weight loss with non-surgical interventions in obese adults: systematic review and meta-analyses of randomised controlled trials. The BMJ, 348, g2646. http://doi.org/10.1136/bmj.g2646 7Feigenbaum, A., Pasternak, S., Zusk, E., Sarid, M., & Vinker, S. (2005, January 29). Influence of intense multidisciplinary follow-up and orlistat on weight reduction in a primary care setting. BMC Family Practice, 6(5). doi:10.1186/1471-2296-6-5 8Heymsfield, S. B., Van Mierlo, C. A. J., Van Der Knaap, H. C. M., Heo, M., & Frier, H. I. (2003). Weight management using a meal replacement strategy: Meta and pooling analysis from six studies. International Journal of Obesity, 27(5), 537-549. doi:10.1038/sj.ijo.0802258 9Ionut, V., Burch, M., Youdim, A., & Bergman, R. N. (2013). Gastrointestinal hormones and bariatric surgery‐induced weight loss. Obesity, 21(6), 1093-1103. doi:10.1002/oby.20364

10Lee, K., Lee, J., Bae, W. K., Choi, J. K., Kim, H. J., & Cho, B. (2009). Efficacy of low-calorie, partial meal replacement diet plans on weight and abdominal fat in obese subjects with metabolic syndrome: A double-blind, randomised controlled trial of two diet plans - one high in protein and one nutritionally balanced. International Journal of Clinical Practice, 63(2), 195-201. doi:10.1111/j.1742-1241.2008.01965.x

  44

11Li, Z., Hong, K., Saltsman, P., DeShields, S., Bellman, M., Thames, G., . . . Heber, D. (2005). Long-term efficacy of soy-based meal replacements vs an individualized diet plan in obese type II DM patients: Relative effects on weight loss, metabolic parameters, and C-reactive protein. European Journal of Clinical Nutrition, 59(3), 411-418. doi:10.1038/sj.ejcn.1602089 12Marraffa J.M. (2015). Dieting Xenobiotics and Regimens. In Hoffman R.S., Howland M, Lewin N.A., Nelson L.S., Goldfrank L.R. (Eds), Goldfrank's Toxicologic Emergencies, 10e. Retrieved October 12, 2016 from http://accesspharmacy.mhmedical.com.ezproxy4.library.arizona.edu/content.aspx?bookid=1163&Sectionid=65094117. 13Medifast. Retrieved from https://www.medifast1.com/index.jsp 14Miras, A. D., & le Roux, C. W. (2013). Mechanisms underlying weight loss after bariatric surgery. Nature Reviews. Gastroenterology & Hepatology, 10(10), 575. doi:10.1038/nrgastro.2013.119 15Ross, L. J., Wallin, S., Osland, E. J., & Memon, M. A. (2016). Commercial very low energy meal replacements for preoperative weight loss in obese patients: A systematic review. Obesity Surgery, 26(6), 1343-1351. doi:10.1007/s11695-016-2167-3 16Shah, N., Greenberg, J. A., Leverson, G., Statz, A. K., Jolles, S. A., & Funk, L. M. (2016). Weight loss after bariatric surgery: A propensity score analysis. Journal of Surgical Research, 202(2), 449-454. doi:10.1016/j.jss.2016.01.041 17Sheehan A, Chen J.T., Yanovski J.A., Calis K (2014). Chapter 121. Obesity. InDiPiro J.T., Talbert R.L., Yee G.C., Matzke G.R., Wells B.G., Posey L (Eds), Pharmacotherapy: A Pathophysiologic Approach, 9e. Retrieved October 12, 2016 from http://accesspharmacy.mhmedical.com.ezproxy4.library.arizona.edu/content.aspx?bookid=689&Sectionid=48811515. 18Shikany, J., Thomas, A., Beasley, T., Lewis, C., & Allison, D. (2013). Randomized controlled trial of the medifast 5 & 1 plan for weight loss. International Journal of Obesity, 37(12), 1571-1578. doi:10.1038/ijo.2013.43 19Sumithran, P., & Proietto, J. (2014, July 27). Benefit-Risk Assessment of Orlistat in the Treatment of Obesity. Drug Safety, 37(8), 597-608. doi:10.1007/s40264-014-0210-7 20Tieken, S., Leidy, H., Stull, A., Mattes, R., Schuster, R., & Campbell, W. (2007). Effects of solid versus liquid meal-replacement products of similar energy content on hunger, satiety, and appetite-regulating hormones in older adults. Horm Metab Res, 39(5), 389-394. doi:10.1055/s-2007-976545 21Torgerson, J. S., Hauptman, J., Boldrin, M. N., & Sjöström, L. (2004). XENical in the prevention of diabetes in obese subjects (XENDOS) study. Diabetes Care, 27(1), 155-161. doi:10.2337/diacare.27.1.155

  45

22Vander Wal, J. S., McBurney, M. I., Cho, S., & Dhurandhar, N. V. (2007). Ready-to-eat cereal products as meal replacements for weight loss. International Journal of Food Sciences and Nutrition, 58(5), 331-340. doi:10.1080/09637480701240802

23Vázquez, C., Montagna, C., Alcaraz, F., Balsa, J. A., Zamarrón, I., Arrieta, F., & Botella- Carretero, J. I. (2009). Meal replacement with a low-calorie diet formula in weight loss maintenance after weight loss induction with diet alone. European Journal of Clinical Nutrition, 63(10), 1226-1232. doi:10.1038/ejcn.2009.48 24Wolfe, B. M., Kvach, E., & Eckel, R. H. (2016). Treatment of obesity: Weight loss and bariatric surgery. Circulation Research, 118(11), 1844-1855. doi:10.1161/CIRCRESAHA.116.307591 25Zohrabian, A. (2010). Clinical and economic considerations of antiobesity treatment: A review of orlistat. ClinicoEconomics and Outcomes Research, 2(1), 63-74.