Manipulating Metabolism: Moving Molehills or Mountains?A Look at Metabolic Effects of Saturated Fats, Refined Carbohydrates & Overeating

s a

nutritionist,

I’ve learned and studied the ins and outs of the body, more

specifically in relation to food and metabolic fuels like glucose

(carbohydrates), lipids (fats) and proteins. I’m acutely aware of how involved

the human body is and how ambiguous and complex the phrase “eat

healthy” can be. Everybody is different, from one’s childhood, lifestyle, and

daily responsibilities (or lack thereof) to how an individual’s body

metabolizes, stores, and expends energy. It may be difficult to appreciate

that these two central components of life are co-dependent; a person’s

dietary lifestyle can affect a person’s overall lifestyle and conversely, a

person’s lifestyle can affect a person’s dietary lifestyle. In an effort to help

guide the muddled path of balanced and healthy eating and better equip any

reader with the tools to achieve one’s personal weight and health goals, I’d

like to focus on and explain three chief aspects of nutrition that most people

are faced with on a daily basis and the potential metabolic effects they can

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have on the human body. Dietary saturated fats (SFA), refined carbohydrates

and overeating are three facets of nutrition that are closely interrelated and

“feed” off of one another. It’s typical that these three categories are

automatically and negatively associated with what not to do or eat. I ask that

any person reading this will ultimately make their own educated decision on

what they consider to be good or bad for themselves and their own personal

lifestyle.

SATURATED FATS

As most people know, nation-wide and otherwise, the United States is

experiencing its highest level of obesity rates ever recorded and, therefore,

higher rates of acute and chronic obesity-related diseases. Metabolic

Syndrome (MetS), one potential cause of the

aforementioned diseases, is defined as high

visceral adipose composition (abdominal obesity) in

conjunction with two of the four following blood

levels: high blood triglycerides, high blood

pressure, high blood glucose, or a low high-density lipoprotein (HDL)

cholesterol ratio to total cholesterol (TC).4 Some health consequences of

MetS are the increased risk of type II diabetes, cardiovascular disease (CVD),

stroke and other obesity-related diseases.4 Unfortunately, the world-wide

population with MetS is 25% which is currently on the rise since “the

prevalence of MetS parallels the rising rates of obesity.”4 This statistic

represents one-fourth of the world – that’s about 1.8 billion people.6 The

most prevalent metabolic dysfunctional characteristic among those with

MetS is insulin resistance (IR) which is even more prevalent in those with

MetS who also have high abdominal obesity.4 Insulin resistance is an

unnatural physiological disorder in which cells and tissues become less

sensitive to the presence of insulin which in turn inhibits glucose from

entering said cells and tissues. Over time, glucose will begin to accumulate

in the blood giving rise to blood glucose levels which can significantly

increase the risk of type II diabetes as well as other obesity-related diseases.

According to studies conducted by Susan Jebb, a professor of diet and

population health in the UK, it was concluded that it is more effective to

decrease energy consumption in order to lose weight than to adjust diet

composition in obese people or those with

obesity-related health issues.4 With that

being said, she also denotes in her findings

that since most overweight and obese people

want to lose weight as well as reduce their

health risks, it is equally important to

address fatty acid composition in one’s diet.4

This acknowledgement leads me to the controversial question asked by

health professionals and laymen, alike, are saturated fats actually bad for

you?

In one research study on the relationship between dietary fatty acids and

the development of obesity, IR, and type II diabetes, conducted by Ulf

Riserus, an associate professor of clinical nutrition and metabolism in

Sweden, it was found that in those with obesity and IR, excess free fatty

acids in the blood were unable to be absorbed and converted into glucose or

stored as triglycerides in the liver, skeletal muscle or adipose tissue.4 This

inability for the liver, muscle and fat tissue to absorb excess free fatty acids

for energy use or storage is what can lead to increased risk of obesity-related

diseases; the body isn’t able to function normally and therefore will react

abnormally and possibly become diseased. Riserus also found in his studies

that the risk of diabetes was inversely proportionate to a diet containing

polyunsaturated fatty acids (PUFAs) and vegetable oils, yet he also stated

that “the effects of different types of dietary fatty acids on obesity and fat

accumulation have not been extensively investigated.” 4

One ongoing debate in the field of nutrition is the controversy between

“good” and “bad” fats and how much a person can consume of each before

health problems arise. The research for and against this subject matter can

get murky given there are several kinds of fats and several ways that they

can be used, stored, or transformed in the body. The research on saturated

fats is difficult to analyze and conduct in human subjects; many research

studies state that their findings are

inconsistent, contradictory and

inconclusive. For instance, one study

conducted on a panel of obese

women who were either insulin-

sensitive or insulin-resistant, in which they were either fed a high

carbohydrate [60% of total energy consumed (E)], low fat (20% E) diet or a

low carbohydrate (40% E), high fat (40%) diet,

found that the insulin-sensitive women who ate

the high carbohydrate diet lost more weight than

the insulin-sensitive women who ate the high fat

diet. Conversely, the insulin-resistant women who

ate the high fat diet lost more weight than the

insulin-resistant women who ate the high carbohydrate diet. Based on this

study, it can be concluded that the state of insulin sensitivity is a large factor

in the metabolic relationship between weight loss and macronutrient

distribution.4 One of the many suggested fat substitutes for saturated fats

are unsaturated fats (both poly- and mono-), however, “data on the effect of

increasing PUFA at the expense of SFA remain limited and inconsistent.”4 It

seems that some research conducted on both animals and humans suggests

that PUFAs improve weight loss, while other studies suggest increasing SFA

composition in the diet to improve weight loss and health benefits. Berthold

Keletzko, a professor at the University of Munich Medical Center in Germany,

found that those in western countries who consume increased amounts of n-

6 PUFA (vegetable oils) and reduced amounts of n-3 PUFA have an increased

risk of obesity and type 2 diabetes.4

In a research study that was conducted to analyze the metabolic effect of

dietary saturated fat on subject’s fat composition and accumulation, it was

found, overall, that those who ate a diet high in saturated fat (24%), as

opposed to the average American diet saturated fat composition (12%) and a

diet low in saturated fat (6%), yielded better cholesterol panels, less fat

accumulation, decreased insulin resistance, and an overall decreased risk for

metabolic dysfunction. The reasoning behind this contradictory support for a

high fat diet with 24% SFA is that a diet this high in saturated fatty acids

contains more medium-chain fatty acids (MCFA) as opposed to long-chain

fatty acids (LCFAs); MCFAs can transport from the intestines directly to the

liver for faster oxidation while LCFAs have to be transported through the

blood first before they can be stored and metabolized by the body.

Additionally, MCFAs are less likely to be stored as adipose tissue due to their

efficient oxidation capabilities once inside a cell.1

REFINED CARBOHYDRATES

There are two kinds of carbohydrates: simple and complex. Their names

are definitive of how easily they are

metabolized in the body; simple

(refined) carbohydrates are easily

oxidized by the body while complex

(unrefined) carbohydrates are oxidized

at a slower rate. Being able to absorb

carbohydrates easily and faster may sound efficient and better for the body,

however, this is not the case. Simple carbohydrates are usually high on the

glycemic index while complex carbohydrates are low; the glycemic index is a

measure of how a food will effect blood glucose and insulin levels. As blood

glucose increases, the release of insulin will increase accordingly since

insulin is the mechanism by which glucose is able to be absorbed into cells to

make ATP (energy). Overtime, if there is enough glucose in the blood, the

body begins to become resistant to insulin which means that glucose can’t

be absorbed into cells and tissues for fuel and will, therefore, begin to

accumulate in the blood causing rise in blood glucose levels.

According to Ludwig, refined carbohydrates have a negative effect on the

body in that they increase energy storage in fat cells which, as a result,

decreases energy expenditure and increases hunger. Additionally, since the

fat cells absorb the energy consumed, there isn’t anything left to circulate or

oxidize in the body which leads the body to believe that it’s

hungry, possibly starving, resulting in overeating.2 In other

words, the body absorbs and utilizes refined carbohydrate

fuel so quickly, their presence as a metabolic fuel in the blood

stream is too short to maintain a feeling of contentment after

eating which leads to increased hunger and food intake.

One study that analyzed metabolic dysfunction in mice as a

result of high refined carbohydrate-containing diets (HC) found that those fed

a HC diet exhibited “acute and sustained increase in visceral adiposity,

glucose intolerance, low insulin sensitivity [insulin resistance] and

hyperlipidemia [high blood lipids]…”5 Within the same study, evidence

showed that even when food intake and body weight were unchanged, the

mice on the HC diet had a significant increase in their visceral adiposity (fat

accumulation on vital organs).5 In another study, obese young adults were

put on either a low fat diet or a low-glycemic-load diet (indicative of complex

carbohydrates). Results indicated that subjects on the low-glycemic-load diet

lost more weight and experienced a decrease in percent body fat more so

than those on the low-fat diet. Researchers deduced from these findings that

“reducing the glycemic load might be especially important for achieving

weight loss in individuals with high insulin secretion.”4 Overall, this study

supports the evidence that high-carbohydrate containing diets made up

mostly of refined carbohydrates (those with a high glycemic index

composition) can drastically increase fat tissue in the body (with or without

weight gain) which is strongly correlated with MetS.5

OVEREATING

There is a misconception understood to be true by some people who are

trying to lose weight that cutting calories is the answer. This method of

weight loss can and is usually successful in

overweight and obese people, however, it is

important to note that an acute decrease in

available fuel in the body can lead to extreme

hunger and increased food intake.2 This is why

dieting isn’t as successful as making a dietary

lifestyle change; people feel limited and cornered when only “allowed” to eat

specific amounts of specific foods. On a psychological level, people,

evolutionarily and naturally, start to resist and do the opposite of what

they’re being told (even within themselves) when they feel like they do not

have choice or control in a situation; this stands true when people address

their dietary habits and composition. People need to have choice and control

over their eating to be successful in the long-run. When people deprive

themselves of food or specific kinds of foods, both a psychological and

physiological effect can occur leading to psychological resistance as well as a

strong physiological drive to eat, which usually leads to indulgences and

overeating.

On a biological and chemical level, without needing to know the exact

chemical structures of carbohydrates, fats or proteins, or the biological

chemical reactions that can occur with or between these macronutrients, the

body is capable of breaking down and absorbing carbohydrates easier than

fats or proteins. This means that when a person eats, the carbohydrates

consumed will be broken down and used up as ATP (energy) first before fat

or protein will be. In the case of overeating, the body can only break down,

absorb and utilize a certain amount of food before it reaches its threshold.

When this threshold is met, the body will store any excess and unnecessary

energy for later use which means fat will be utilized secondarily, if at all,

resulting in fat accumulation throughout the body. As a note, protein isn’t

our focus in this analysis of macronutrient oxidation and storage because it

is the third and last macronutrient to be used as fuel by the body.

In a study published in The New England Journal of Medicine, researching

the effects diet and lifestyle can have on long-term weight gain, it was

suggested that “dietary quality (the types of foods and beverages

consumed) influences dietary quantity (total calories).”3 These findings were

further supported by the positive correlation observed between increased

consumption of starches and refined carbohydrates with weight gain.3

Ultimately, with overeating, it’s important to consider both the diet

composition, mostly focusing on dietary fats and carbohydrates consumed,

as well as the amount of energy consumed as to not consume more energy

than expended on a daily basis.

FOOD FOR THOUGHT

The body is a tricky, messy, intricate web of

chemical and biological reactions that are meant to

keep everything in balance to keep us healthy and

alive, however, as we’ve learned, our part in this equation is not that simple.

We, as humans, are perfectly imperfect and it is our duty, to the best of our

abilities, to feed our bodies appropriately so that we can continue living on in

this world and fulfill our individual purposes in life. Simply existing is one of

the greatest gifts you can give someone you love and when you get down to

it, dismissing the mundane and confusing scientific aspects of nutrition, diet

and lifestyle are two of the most important facets of life that can give you as

well as others the gift of life. Be kind to yourself and never give up.

“You never fail until you stop trying.” – Albert Einstein

REFERENCES

1. Enos RT, Davis JM, Valazquez KT, et al. Influence of dietary saturated fat content on adiposity, macrophage behavior, inflammation, and metabolism: composition matters. Journal of Lipid Research. 2013; 54: 152-163. doi: 10.1194/jlr.M030700

2. Ludwig DS, Friedman MI. Increasing adiposity: consequence or cause of overeating?. JAMA. 2014; 311 (21): 2167-2168. doi:10.1001/jama.2014.4133.

3. Mozaffarian D, Hao T, Rimm EB, Willett WC, Hu FB. Changes in diet and lifestyle and long-term weight gain in women and men. The New England Journal of Medicine. 2011; 364 (25): 2392-2404. doi: 10.1056/NEJMoa1014296

4. Nettleton JA, Jebb S, Riserus U, Koletzko B, Fleming J. Role of dietary fats in the prevention and treatment of the metabolic syndrome. Annals of Nutrition & Metabolism. 2014; 64: 167-178. doi: 10.1159/000363510.

5. Oliveira MC, Menezes-Garcia Z, Henriques MCC, et al. Acute and sustained inflammation and metabolic dysfunction induced by high refined carbohydrate-containing diet in mice. Obesity. 2013; 21 (9): E396–E406. doi: 10.1002/oby.20230/

6. U.S. and world population clock. United States Census Bureau. 2015; Available from: http://www.census.gov/popclock/