body composition and nutrition for health

Scott K. Powers • Edward T. HowleyScott K. Powers • Edward T. HowleyScott K. Powers • Edward T. HowleyScott K. Powers • Edward T. Howley

Theory and Application to Fitness and PerformanceTheory and Application to Fitness and PerformanceSEVENTH EDITION

Chapter

Presentation prepared by:

Brian B. Parr, Ph.D.

University of South Carolina Aiken

Copyright ©2009 The McGraw-Hill Companies, Inc. Permission required for reproduction or display outside of classroom use.

Body Composition and Body Composition and Nutrition for HealthNutrition for Health

Chapter 18

Copyright ©2009 The McGraw-Hill Companies, Inc. All Rights Reserved.

ObjectivesObjectives

1. Identify the U.S. Dietary Goals relative to (a) carbohydrates and fats as a percent of energy intake, (b) salt and cholesterol, and (c) saturated and unsaturated fats.

2. Contrast the Dietary Goals with the Dietary Guidelines.

3. Describe what is meant by the terms Recommended Dietary Allowance (RDA) and Dietary Reference Intakes (DRIs), and how they relate to the Daily Value (DV) used in food labeling.

4. List the classes of nutrients.

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5. Identify the fat- and water-soluble vitamins, describe what toxicity is, and identify which class of vitamins is more likely to cause this problem.

6. Contrast major minerals with trace minerals, and describe the role of calcium, iron, and sodium in health and disease.

7. Identify the primary role of carbohydrates, two major classes, and the recommended changes in the American diet to improve health status.

8. Identify the primary role of fat and the recommended changes in the American diet to improve health status.

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9. List the food groups represented in the MyPyramid eating plan.

10.Describe the Dietary Approaches to Stop Hypertension (DASH) eating plan, and describe similarities to the MyPyramid plan.

11.Describe the limitation of the height/weight table in determining overweight and obesity.

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12.Provide a brief description of the following methods of measuring body composition: isotope dilution, photon absorptiometry, potassium-40, hydrostatic (underwater weighing), dual energy x-ray absorptiometry, near infrared interactance, radiography, ultrasound, nuclear magnetic resonance, total body electrical conductivity, bioelectrical impedance analysis, air displacement plethysmography, and skinfold thickness.

13.Describe the two-component model of body composition and the assumptions made about the density values for the fat-free mass and the fat mass; contrast this with the multicomponent model.

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ObjectivesObjectives14.Explain the principle underlying the measurement

of whole-body density with underwater weighing, and why one must correct for residual volume.

15.Explain why there is an error of ±2.0% in the calculation of percent body fat with the underwater weighing technique.

16.Explain how a sum of skinfolds can be used to estimate a percent body fatness value.

17.List the recommended percent body fatness values for health and fitness for males and females, and explain the concern for both high and low values.

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18.Discuss the reasons why the average weight at any height (fatness) has increased while deaths from cardiovascular diseases have decreased.

19.Distinguish between obesity due to hyperplasia of fat cells and that due to hypertrophy of fat cells.

20.Describe the roles of genetics and environment in the development of obesity.

21.Explain the set point theory of obesity, and give an example of a physiological and behavioral control system.

22.Describe the pattern of change in body weight and caloric intake over the adult years.

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23.Discuss the changes in body composition when weight is lost by diet alone versus diet plus exercise.

24.Describe the relationship of the fat-free mass and caloric intake to the BMR.

25.Define thermogenesis and explain how it is affected by both short- and long-term overfeeding.

26.Describe the effect of exercise on appetite and body composition.

27.Explain quantitatively why small differences in energy expenditure and dietary intake are important in weight gain over the years.

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OutlineOutline

Nutritional Goals Standards of

Nutrition Classes of Nutrients

Water

Vitamins

Minerals

Carbohydrates

Fats

Protein

Meeting the Guidelines and Achieving the GoalsFood Group Plans

Evaluating the Diet

Body CompositionMethods of Assessing Overweight and Obesity

Methods of Measuring Body Composition

Two-Component System of Body Composition

Body Fatness for Health and Fitness

Obesity and Weight ControlObesity

Diet, Exercise, and Weight ControlEnergy and Nutrient Balance

Diet and Weight Control

Energy Expenditure and Weight Control

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U.S. Dietary Goals (1977)U.S. Dietary Goals (1977)

• Increase carbohydrate intake to 55–60% total calories• Decrease fat intake to less than 30% total calories

– Decreased saturated fat to less than 10% total calories

– Increase polyunsaturated and monounsaturated fat to 10% of caloric intake

• Decrease dietary cholesterol to 300 mg per day• Reduce sugar consumption to 15% total calories• Decrease salt intake to 3 grams per day

Nutritional Goals

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Meeting the U.S. Dietary Goals Meeting the U.S. Dietary Goals

• Increase intake of fruits, vegetables, and whole grains• Increase consumption of poultry and fish

– Decrease intake of meat• Decrease intake of foods high in fat

– Substitute polyunsaturated fat for saturated fat• Substitute nonfat milk for whole milk• Decrease consumption of butter, fat, eggs, and other

high-cholesterol foods• Decrease consumption of sugar and foods high in

sugar• Decrease consumption of salt and foods high in salt

Nutritional Goals

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Dietary Guidelines for Dietary Guidelines for Americans (1980) Americans (1980)

• Did not provide specific quantities to achieve for fat, cholesterol, salt, and carbohydrates

• More general statements for good health

Nutritional Goals

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Institute of Medicine Dietary Institute of Medicine Dietary Recommendations (2002)Recommendations (2002)

• 45–65% calories from carbohydrates

• 20–35% calories from fat– Infants and younger children need higher

proportion of fat (25–40%)

• 10–35% from protein

Nutritional Goals

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Dietary Guidelines for Dietary Guidelines for Americans (2005)Americans (2005)

• Consume a variety of nutrient-dense foods and beverages within and among the basic food groups

• Choose foods that limit the intake of saturated and trans fats, cholesterol, added sugars, salt, and alcohol

• Maintain body weight in a health range– Balance calories from foods and beverages with

calories expended– Engage in regular physical activity and reduce

sedentary activities

Nutritional Goals

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Clinical Applications 18.1Clinical Applications 18.1

Institute of Medicine ReportInstitute of Medicine Report• Established RDA for carbohydrate

– 130 g/day (meets glucose needs of brain)• AI (adequate intake) for fiber set

– 38 g/day (men) and 25 g/day (women)• AI for linoleic acid (omega-6 fatty acid)

– 17 g/day (men) and 12 g/day (women)• AI for -linolenic acid (omega-3 fatty acid)

– 1.6 g/day (men) and 1.1 g/day (women)• Maintained adult protein requirement

– 0.8 g/kg body weight/day• AI for water set

– 3.7 L/day (men) and 2.7 L/day (women)

Nutritional Goals

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In SummaryIn Summary

Current recommendations for the distribution of calories in foods include a broad range, rather than a single goal: carbohydrates: 45% to 65%, fats: 20% to 35%, and proteins: 10% to 35%.

The publication, Dietary Guidelines for Americans, has been revised over time to reflect new science and to deal with nutrition (and physical activity) and health-related issues. The 2005 edition provides recommendations to meet the new nutritional standards with special focus on achieving energy balance.

Nutritional Goals

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Dietary Reference Intakes Dietary Reference Intakes (DRIs)(DRIs)

• Quantity of nutrients needed for proper function and health

• Recommended Daily Allowances (RDA)– Quantity of each nutrient to meet the needs of nearly

all (97–98%) healthy persons• Adequate Intakes (AI)

– Recommended daily intake based on apparently healthy people

• Tolerable Upper Intake Level (UL)– The highest intake level that is likely to pose no risk

• Estimated Average Requirement (EAR)– The intake estimated to meet requirements of half of

healthy people

Standards of Nutrition

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Standards of NutritionStandards of Nutrition

• Estimated Energy Requirement (EER)– Average dietary energy intake predicted to

maintain energy balance considering age, gender, weight, height, and level of physical activity

• Daily Value (DV)– Standard used in nutritional labeling– Percentage of recommended intake in each

serving• Based on a 2,000 kcal•day–1 diet


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Nutritional LabelingNutritional Labeling

• Food labels contain:– Serving size information– Total calories and fat calories– Total fat grams, saturated fat grams,

cholesterol, and the %DV for each• Based on a 2,000-calorie diet

– Total carbohydrate and its sources– Percent of DV for vitamins and minerals

• Sodium is given special attention


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Example of a Food LabelExample of a Food Label


Figure 18.1

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The Recommended Dietary Allowance (RDA) is the quantity of a nutrient that will meet the needs of almost all healthy persons.

The Daily Value (DV) is a standard used in nutritional labeling.


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WaterWater

• Absolutely essential for life– Loss of only 3–4% body water affects performance

• Water loss– Normally ~2500 ml per day– Temperature and exercise can increase water loss to

6–7 liters per day• Water intake

– Beverages (1500 ml)– Solid food (750 ml)– Metabolic processes (250 ml)– AI is 2.7 L/day (women), 3.7 L/day (men)

Classes of Nutrients

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VitaminsVitamins• Fat-soluble vitamins

– A, D, E, K

– Can be stored in the body

– Excess intake can be toxic

• Water-soluble vitamins

– B vitamins

• Thiamin (B-1), riboflavin (B-2), niacin, pyroxidine (B-6), folic acid, B-12, pantothenic acid, and biotin

• Involved in energy metabolism

– Vitamin C

• Maintenance of bone, cartilage, and connective tissue


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Summary of the Fat-Soluble Summary of the Fat-Soluble VitaminsVitamins


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Summary of the Water-Soluble Summary of the Water-Soluble VitaminsVitamins


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The fat-soluble vitamins include A, D, E, and K. These can be stored in the body in large quantities, and a toxicity can develop.

The water-soluble vitamins include thiamin, riboflavin, niacin, B6, folic acid, B12, pantothenic acid, biotin, and C. Most of these are involved in energy metabolism. Vitamin C is involved in the maintenance of bone, cartilage, and connective tissue.


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Classes of Nutrients—MineralsClasses of Nutrients—Minerals

Major minerals• Calcium• Sodium• Phosphorus• Magnesium• Sulfur• Potassium• Chloride

Trace elements• Iron• Iodine• Fluoride• Zinc• Selenium• Copper• Cobalt• Chromium• Manganese• Molybdenum• Arsenic• Nickel• Vanadium


• For a summary of minerals, see Table 18.2

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MineralsMinerals

• Calcium– Important in teeth and bone structure

• Osteoporosis

• Iron– Component of hemoglobin

• Anemia

• Sodium– Associated with hypertension

• In sodium-sensitive individuals


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In SummaryIn Summary The major minerals include calcium,

phosphorus, magnesium, sulfur, sodium, potassium, and chloride. The trace elements include iron, iodine, fluoride, zinc, selenium, copper, cobalt, chromium, manganese, molybdenum, arsenic, nickel, and vanadium.

Inadequate calcium and iron intake have been linked with osteoporosis and anemia, respectively. Those with a genetic predisposition for hypertension due to sodium retention benefit from a reduction in salt intake.


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CarbohydratesCarbohydrates

• Sugars and starches– Contain 4 kcal/g – Major energy source

• Crucial for red blood cells and neurons

– Recommendations• Choose or prepare foods and beverages with little

added sugars or caloric sweeteners• Reduce the incidence of dental caries by

consuming sugar-containing foods and beverages less frequently


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CarbohydratesCarbohydrates• Dietary fiber

– Non-digestible carbohydrates and lignin• Reduces transit time in intestine• Soluble fiber linked to lower serum cholesterol

• Functional fiber– Non-digestible carbohydrates

• Have beneficial physiological functions• Recommendations

– AI: 38 g/day for men, 25 g/day for women– Increase dietary fiber and complex carbohydrate

intake– Decrease simple sugar intake


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Clinical Applications 18.2Clinical Applications 18.2Glycemic Index—What Is It and Is It Important?Glycemic Index—What Is It and Is It Important?

• Glycemic index (GI)– Blood glucose response (over 2 hours) to

carbohydrate food – Low GI foods make blood glucose regulation less

challenging• Glycemic load (GL)

– Takes into account amount of food eaten• Can be used to plan meals

– Improved metabolic control in diabetics– Reduce cholesterol and vascular inflammation

• Simplicity complicated by protein and fat in diet


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FatsFats

• Important energy source– Contain 9 kcals•gram–1

• Triglycerides

• Phospholipids

• Cholesterol– Low-density lipoproteins (LDLs)

• Directly related to cardiovascular disease risk• Increased by diets high in saturated fat

– High-density lipoproteins (HDLs)• Protect against heart disease


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FatsFats

• Recommendations– Consume less than 10% calories from saturated

fats and less than 300 mg/day cholesterol– Keep total fat intake between 20–35% calories

• Most fats should come from polyunsaturated and monounsaturated fats

– Choose and prepare meat, poultry, dry beans, milk, and milk products that are lean, low fat, or fat free

– Limit intake of fat and oils high in saturated and/or trans fatty acids


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Diet Composition and Diet Composition and Syndrome XSyndrome X

• Clustering of risk factors associated with cardiovascular disease risk– Hyperinsulinemia, hyperlipidemia, hypertension, and

obesity

• Diet composition may be a contributing factor– A high-fat, refined sugar (HFS) diet associated with:

• Insulin resistance in elevated plasma insulin• Elevated triglycerides• Larger fat cell size• Higher blood pressure

– Compared to low-fat, complex-carbohydrate diet


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ProteinsProteins

• Not a major source of energy– 4 kcals•gram–1

• High-quality proteins contain the nine essential amino acids– Cannot be synthesized by the body

• Most Americans meet protein intake requirements– 0.8 grams•kg–1 body weight– Requirements may be higher in athletes


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Carbohydrate is a primary source of energy in the American diet and is divided into two classes: that which can be metabolized (sugars and starches) and dietary fiber.

Two recommendations to improve health status in the American population are to consume complex carbohydrates to represent about 45% to 65% of the calories, and to add more dietary fiber.


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Americans consume too much saturated fat, and the recommended change is to reduce this to no more than 10% of the total calories. Trans fat intake should be reduced as much as possible, and most fat intake should come from sources containing polyunsaturated and monounsaturated fatty acids.

The protein requirement of 0.8 g/kg can be met with low-fat selections to minimize fat intake.


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Meeting the Guidelines and Meeting the Guidelines and Achieving the GoalsAchieving the Goals

• The new Dietary Guidelines for Americans describes a healthy diet as one that:– Emphasizes fruits, vegetables, whole grains,

and fat-free or low-fat milk and milk products– Includes lean meats, poultry, fish, beans,

eggs, and nuts

– Is low in saturated fat, trans fat, cholesterol, salt (sodium), and added sugars

Meeting the Guidelines and Achieving the Goals

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Food Group PlansFood Group Plans

• Basic Four Food Group Plan– Meat and meat substitutes– Milk and milk products– Fruits and vegetables– Grains (breads and cereals)

• Foods should have a high nutrient density– Nutrient content in 1,000 kcal of a food


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MyPyramid (2005)MyPyramid (2005)

• Revision of 1992 Food Guide Pyramid• Includes major food groups

– Grains, vegetables, fruits, milk, and meat & beans– How much of each category needed to meet 2000

kcal/day energy expenditure

• Special attention on physical activity• Website provides individualized dietary plan

– Based on age, gender, and level of physical activity

• Consistent with most dietary recommendations– Should help control health conditions– Vitamin E and potassium intake may be too low


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MyPyramid Food GroupsMyPyramid Food Groups


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Dietary Approaches to Stop Dietary Approaches to Stop Hypertension (DASH)Hypertension (DASH)

• Developed to prevent hypertension and to lower blood pressure in those with hypertension

• Healthy eating approach consistent with good health:– Reducing cardiovascular risk factors– Achieving and maintaining a healthy body

weight


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The DASH Eating PlanThe DASH Eating Plan


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Evaluating the DietEvaluating the Diet

• How well is someone achieving the guidelines?

• 24-hour recall method– Remember what you ate the previous 24

hours

• Food records– Person records what they eat– Recommended to use 3–4 days in a week


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The 2005 Dietary Guidelines for Americans identified two approaches to use to meet dietary standards and achieve a healthy body weight: The U.S. Department of Agriculture’s MyPyramid

promotes a personalized approach to healthy eating and physical activity. It replaced the Food Guide Pyramid.

The Dietary Approaches to Stop Hypertension (DASH) food plan is suitable for all to use in planning a healthy diet, whether one has hypertension or not.


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Methods of Assessing Overweight Methods of Assessing Overweight and Obesityand Obesity

• Metropolitan Life Insurance height and weight tables– No longer widely used

• Body mass index (BMI)– Weight (kg) / height (m2)– Classification for adults

• Underweight: BMI <18.5 kg/m2

• Normal: BMI 18.5–24.9 kg/m2

• Overweight: BMI 25.0–29.9 kg/m2

• Obesity: BMI ≥30.0 kg/m2

– No way to tell actual body composition• A very muscular person could be classified as obese

Body Composition

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Methods of Measuring Body Methods of Measuring Body CompositionComposition

• Isotope dilution– Measurement of total body water– Uses an isotope of water

• Photon absorptiometry– Determines mineral content and density of bones

• Potassium-40– Measurement of lean tissue

• Hydrostatic (underwater) weighing– Determination of body density

• Dual energy X-ray absorptiometry (DEXA)– Estimates lean tissue, bone, mineral, and fat

Body Composition

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• Near infrared interactance (NIR)– Uses an infrared light beam

• Radiography– Measurement of fat width

• Ultrasound– Measures thickness of subcutaneous fat

• Nuclear Magnetic Resonance (NMR)– Volumes of specific tissues

• Total body electrical conductivity (TOBEC)– Electrical conductivity of lean and fat tissue

Body Composition

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• Bioelectrical impedance analysis (BIA)– Measurement of total body water and fatness

• Air displacement plethysmography– Measurement of body density

• Skinfold thickness– Estimate of total body fatness

Body Composition

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Body Composition AssessmentBody Composition Assessment• Four-component model

– Mineral, water, protein, and fat– Best estimates of percent fat

• Three-component model– Body water, protein + mineral, and fat– Body water + protein, mineral, and fat– Accounts for variations in bone density or body

water

• Two-component model– Fat mass and fat-free mass– Most commonly used method

Body Composition

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The BMI uses a simple ratio of weight-to-height squared (kg/m2) to classify individuals as being normal weight, overweight, or obese. However, just like the old height-weight tables, the BMI does not consider the composition of the body weight (i.e., proportion of muscle tissue vs. fat tissue).

Body composition can be measured in terms of total body water (isotope dilution, bioelectric impedance analysis), bone density (photon absorptiometry), lean tissue mass (potassium-40), density (underwater weighing, air displacement plethysmography), and thickness of various tissues (ultrasound, radiography, skinfolds).

Body Composition

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Body composition assessment can be based on four-component (mineral, water, protein, and fat), three-component (body water, protein+mineral, and fat, or body water+protein, mineral, and fat), or two-component (fat-free mass and fat mass) models. The four-component model is the most accurate.

Body Composition

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• Body divided into fat-free and fat mass– Fat mass

• Density = 0.900– Fat-free mass

• Density = 1.100• Measurement of whole-body density

– Underwater weighing– Skinfolds

• Equation to convert body density to percent fat – Based on age, gender, and race– Siri equation:

Two-Component System of Two-Component System of Body CompositionBody Composition

% body fat = 495

Density– 450

Body Composition

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Estimating % Fat from Body Estimating % Fat from Body DensityDensity

Body Composition

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Underwater WeighingUnderwater Weighing

• Density = mass / volume• Measurement of body volume

– Subject is submerged in tank of water– Weight of water displaced = loss of weight when

submerged (Ma – Mw)

– Weight of water displaced is divided by density of water (DW) to calculate volume of water displaced

– Volume is corrected for residual lung volume (VR) and gas in intestinal tract (VGI)

D = MV

– VR – VGI

MA

(MA – MW)=

(DW)

Body Composition

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The Underwater Weighing The Underwater Weighing TechniqueTechnique

Body Composition

Figure 18.2

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In the two-component system of body composition analysis, the body is divided into fat-free and fat mass, with densities of 1.100 and 0.900, respectively. The estimate of the density of the fat-free mass must account for the differences that exist in various populations (i.e., children and African Americans).

Body Composition

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In SummaryIn Summary Body density is equal to mass ÷ volume. Underwater

weighing is used to determine body volume using the principle of Archimedes: When an object is placed in water, it is buoyed up by a counterforce equal to the water it displaces. One can measure the actual volume of the water displaced, or the loss of weight while underwater. The weight of water is divided by the density of water to yield body volume, which must then be corrected for the residual volume and the volume of gas in the GI tract.

The percent body fat value has an error of about ±2.0% due to the normal biological variation of the fat-free mass.

Body Composition

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SkinfoldsSkinfolds

• Prediction of body density from estimation of subcutaneous fat

• Thickness of subcutaneous fat is measured– Specific sites on the body based on age, gender, and

race• Body density is calculated using equations

– Generalized or specific equations• Percent body fat calculated from body density

– Using Siri equation

Body Composition

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Prediction of % Fat Based on SkinfoldsPrediction of % Fat Based on Skinfolds

Body Composition

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Body Fatness for Health and Body Fatness for Health and FitnessFitness

• Recommended body fatness– Males

• 10–20%– Females

• 15–25%• Health concerns above and below these values

– Obesity– Anorexia nervosa and bulimia nervosa

• Calculation of optimal weight

Body Composition

Optimal weight = Fat-free weight

(1 – optimal % fat)

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Subcutaneous fat can be “sampled” as skinfold thicknesses, and a sum of skinfolds can be converted to a percent body fat with formulas derived from the relationship of the sum of skinfolds to a body composition standard based on a two-, three-, or four-component models.

The recommended body fatness for males is 10% to 20%, and for females is 15% to 25%. There is concern about obesity and anorexia for those above and below these values, respectively.

Body Composition

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ObesityObesity• Diseases linked to obesity:

– Hypertension– Type 2 diabetes– Coronary heart disease (CHD)– Stroke– Gallbladder disease– Osteoarthritis– Sleep apnea and respiratory problems– Some cancers

• Endometrial, breast, prostate, colon

– Other health conditions

Obesity

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ObesityObesity

• Prevalence of overweight and obesity in U.S. adults (2004)– 32.2% are obese (BMI ≥30)– 66.3% are overweight (BMI ≥25)

• Includes those classified as obese – Higher in some ethnic groups– 16.5% of U.S. children are overweight

• Distribution of body fat is important– Higher risk of CVD with abdominal obesity

• Waist circumference >102 cm (men) and >88 cm (women)

• Waist to hip ratio >0.95 (men) and >0.80 (women)

Obesity

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Fat Cell Size vs. Number and ObesityFat Cell Size vs. Number and Obesity

• 25 billion fat cells in normal-weight individual– 60–80 billion in obese individual

• During weight loss– Fat cell size decreases, not fat cell number

• Severe obesity (fat mass >30 kg)– Due to increase in fat cell number (hyperplasia)

• Less severe obesity– Due to increase in fat cell size (hypertrophy)

• Hyperplasia – Associated with greater difficulty losing weight and

maintaining weight loss

Obesity

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Relationship Between Fat Cell Size and Fat Relationship Between Fat Cell Size and Fat Cell Number to Total Body FatCell Number to Total Body Fat

Obesity

Figure 18.3

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Causes of Obesity Causes of Obesity

• Genetic factors– Account for about 25% of the transmissible

variance for fat mass and percent body fat– Affects components of energy expenditure

• Amount of spontaneous physical activity• Resting metabolic rate• Thermic effect of food• Relative rate of carbohydrate and fat oxidation

• Cultural factors– Account for about 30%

Obesity

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In SummaryIn Summary Obesity is associated with an increased mortality

from cardiovascular disease and some types of cancer, but being overweight is not. Emphasis should be on maintaining or reducing weight in the overweight individual to decrease the chance of migration to the obese category.

Obesity associated with fat mass in excess of 30 kg is due primarily to an increase in fat cell number, with fat cell hypertrophy being related to smaller degrees of obesity. Those with hyperplasia have a more difficult time losing weight and keeping it off.

Genetic factors account for about 25% of the transmissible variance for fat mass and percent body fat; culture accounts to 30%.

Obesity

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Set Point and ObesitySet Point and Obesity

• Set point theory– Biological set point for body weight much like the set

points for other physiological variables• Physiological set point model

– Biological signals provide input to hypothalamus• Blood glucose, lipid stores, weight on feet

– Food intake is either increased or decreased to maintain body weight

• Cognitive set point model– Cognitive signals about perception of body weight– Influences food intake to maintain body weight

Obesity

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Physiological Set Point Model Physiological Set Point Model for Control of Body Weightfor Control of Body Weight

Obesity

Figure 18.4

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Cognitive Set Point for Control of Cognitive Set Point for Control of Body WeightBody Weight

Obesity

Figure 18.5

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Clinical Applications 18.4Clinical Applications 18.4Drugs, Dietary Supplements, and Weight LossDrugs, Dietary Supplements, and Weight Loss

• Little evidence that dietary supplements work• Drugs, if they work, may have side effects

– Fen-phen promoted weight loss but caused:• Pulmonary hypertension• Heart valve abnormalities• Electrocardiographic abnormalities

• Key points– Focus of weight loss programs should be long-term diet

and exercise behaviors– Most drugs are for short-term use only– If all the diet books, pills, and supplements worked,

obesity would not be a problem

Obesity

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Investigators have proposed a set-point theory to explain obesity given the tendency for people who diet to return to their former weight. Theories based on weight sensors (ponderostatic), the blood glucose concentration (glucostatic), and the mass of lipid (lipostatic) have been proposed.

A behavioral set-point theory has been proposed that relies on the person making appropriate activity and dietary judgments when body weight, size, or shape does not match up with that person’s ideal.

Obesity

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• Static energy balance– Increase intake of 250 kcals•day–1 would lead to

14-pound weight gain over one year

• Dynamic energy balance– Increase in energy intake results in increased

body weight• Energy expenditure also increases, and weight is

maintained at a new, higher level– Results in weight gain of only 3.5 pounds in a year

rate of change of energy stores

rate of change of energy intake

rate of change ofenergy expenditure

= –

Energy BalanceEnergy Balance

change of energy stores

energy intake

energy expenditure

= –

Diet, Exercise, and Weight Control

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The dynamic energy balance equation correctly expresses the dynamic nature of changes in energy intake and body weight. An increase in energy intake leads to an increase in body weight; in turn, energy expenditure increases to eventually match the higher energy intake. Body weight is now stable at a new and higher value.


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Nutrient BalanceNutrient Balance

• Carbohydrate and protein– Excess intake is oxidized– Body regulates expenditure to match intake– Does not contribute to weight gain

• Fat– Excess intake is not necessarily oxidized– Fat expenditure depends on total energy

expenditure – Contributes to weight gain


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The Food QuotientThe Food Quotient

• Food quotient (FQ)– Indicates the mix of CHO and fat in the meal

• 1.00 = 100% CHO• 0.85 = 50% CHO, 50% fat• 0.70 = 100% fat

• Respiratory quotient (RQ)– Indicates the mix of CHO and fat oxidized

• Similar to FQ


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The FQ, RQ, and Nutrient BalanceThe FQ, RQ, and Nutrient Balance

• RQ = FQ– Nutrient balance– RQ/FQ ratio = 1.0

• RQ > FQ– Not oxidizing as much fat as consumed– RQ/FQ ratio > 1.0

• RQ < FQ– Using more fat than is consumed– RQ/FQ ratio < 1.0


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Relationship Between the RQ/FQ Ratio and Relationship Between the RQ/FQ Ratio and Energy BalanceEnergy Balance


Figure 18.6

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Nutrient balance exists for both protein and carbohydrate. Excess intake is oxidized and is not converted to fat.


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Diet and Weight ControlDiet and Weight Control

• Diets high in fat are linked to obesity– Fat grams contain twice as many calories as

carbohydrates– Nutrient balance can most easily be achieved with a

low-fat diet• Calories count and must be considered!• Adherence to the diet is more important than the type of

diet followed• Calories from foods and beverages should be balanced

with calories expended– Gradually decrease caloric intake and increase

physical activity


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Physical Activity for Weight ControlPhysical Activity for Weight Control

• To reduce the risk of chronic disease– 30 minutes of moderate-intensity physical

activity on most days of the week

• To manage weight and prevent gradual weight gain– 60 minutes of moderate- to vigorous-intensity

activity on most days of the week

• To sustain weight loss– 60–90 minutes of moderate-intensity physical

activity


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Diets with a high fat-to-carbohydrate ratio are linked to obesity. Nutrient balance for fat can be most easily achieved with a low-fat diet (high FQ).

Calories do count, and they must be considered in any diet aimed at achieving or maintaining a weight loss goal.


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Energy Expenditure and Weight ControlEnergy Expenditure and Weight Control

• Basal metabolic rate (BMR)– Rate of energy expenditure under standardized

conditions• Supine position, immediately after rising, 12–18 hours

following a meal • Similar to resting metabolic rate (RMR)

– Represents 60–75% total energy expenditure• Lower in women, declines with age• Related to fat-free mass

– Reduced in response to reduced caloric intake (dieting or fasting)

• Exercise can maintain BMR


Chapter 18


Decrease in Basal Metabolic Decrease in Basal Metabolic Rate During Semi-StarvationRate During Semi-Starvation


Figure 18.7

Chapter 18


In SummaryIn Summary The BMR represents the largest

fraction of total energy expenditure in sedentary persons. The BMR decreases with age, and women have lower BMR values than men.

The fat-free mass is related to both the gender difference and to the decline in BMR with age. A reduction in caloric intake by dieting or fasting can reduce the BMR, while physical activity is important in maintaining it.


Chapter 18


Energy Expenditure and Weight Energy Expenditure and Weight ControlControl

• Thermogenesis– “Heat generation” – Thermic effect of feeding

• Increased energy expenditure following ingestion of meals

• Small part of total energy expenditure (10–15%)• Not predictive of obesity

– Brown adipose tissue• Increases heat production in response to norepinephrine

and thyroid hormones– Energy wasteful systems or futile cycles

• Metabolic cycles (Na+/K+ pump activity)


Chapter 18



Thermogenesis (heat generation) is associated with the ingestion of meals (thermic effect of feeding), brown adipose tissue, and “futile cycles.”

The thermic effect of food represents a small part of total energy expenditure and is not predictive of obesity.


Chapter 18


Energy Expenditure and Weight Energy Expenditure and Weight ControlControl

• Physical activity and exercise– Includes exercise and occupational physical

activity– Accounts for 5–40% total energy expenditure

• Depends on activity level

– Important in determining obesity• Inverse relationship between physical activity and

percent fat• Individuals accumulating more than 10,000 steps

per day are more likely to be in “normal” BMI range


Chapter 18


Relationship Between Body Relationship Between Body Fatness and Nonbasal Energy Fatness and Nonbasal Energy

ExpenditureExpenditure


Figure 18.8

Chapter 18


Clinical Applications 18.5Clinical Applications 18.5A Calorie Is a CalorieA Calorie Is a Calorie

• In most studies, diet results in more weight loss than exercise– Is a calorie of exercise equal to a calorie of diet

restriction?• Study by Ross, et al.

– Deficit of 700 kcal/day• Through exercise or diet

– Both treatments lost 16.5 lbs—exactly what was predicted

• Exercise group lost more fat and preserved muscle

• Similar results in another study– Equal caloric deficit through diet alone vs. diet plus

exercise


Chapter 18


Pattern of Caloric Intake for Rats Pattern of Caloric Intake for Rats Versus the Durations of ExerciseVersus the Durations of Exercise


Figure 18.9

Chapter 18


Effect of Exercise on AppetiteEffect of Exercise on Appetite

• Most humans– Energy intake is increased across a broad

range of energy expenditure– Maintains body weight

• Formerly sedentary individuals– Net loss of appetite on an exercise program– Facilitates weight loss


Chapter 18


Pattern of Pattern of Caloric Caloric Intake Intake Versus Versus

OccupatioOccupational Activitynal Activity


Figure 18.10

Chapter 18


Exercise and Body CompositionExercise and Body Composition

• Individuals who exercise generally have lower body weight and percent fat

• Weight loss in conjunction with exercise– Less lean body mass is lost– More fat mass is lost

• In general, those doing the largest amount of physical activity had the largest changes in percent body fat


Chapter 18



Humans increase appetite over a broad range of energy expenditure to maintain body weight; however, formerly sedentary individuals show a net loss of appetite when they undertake an exercise program.

When weight loss occurs with an exercise and diet program, less lean body mass is lost than when the same weight loss is achieved by diet alone.


Chapter 18


Exercise, Weight Loss, and Weight Exercise, Weight Loss, and Weight MaintenanceMaintenance

• Weight loss– Exercise contributes a small fraction to weight loss

• Weight maintenance– Light to moderate exercise

• Fats make up a large fraction of energy expended– Moderate exercise

• Expends large amounts of fat and calories• Fitness and weight-loss goals

– Vigorous exercise• Effective in expending calories and achieving fitness

and fat-loss goals


Chapter 18


Clinical Applications 18.6Clinical Applications 18.6Successful Losers—How Much Exercise Is Needed Successful Losers—How Much Exercise Is Needed

to Keep the Weight Off?to Keep the Weight Off?

• To maintain weight and prevent weight gain– 60 min per day of moderate-intensity exercise

• To sustain weight loss:– 60–90 min/day of moderate-intensity exercise

• National Weight Control Registry “successful losers”– Average weight loss of 30 kg for 5.5 years– No evidence of psychological distress– Limited caloric intake to 1,400 kcal/day with 25%

calories from fat– Expended 400 kcal/day through physical activity


Chapter 18



Successful Losers—How Much Successful Losers—How Much Exercise is Needed to Keep the Exercise is Needed to Keep the

Weight Off?Weight Off?• Strategies for long-term weight loss (NWCR)– Engaging in high-level physical activity– Eating a diet low in calories and fat– Consistent eating plan, including breakfast– Self-monitoring weight regularly– Catching slips before they result in weight

regain


Chapter 18



Moderate-intensity exercise is an appropriate choice for most Americans to achieve health-related and weight-loss goals. Plasma free fatty acids make up a large fraction of the energy supply for that level of physical activity.

Moderate exercise promotes the expenditure of large amounts of fat and calories, consistent with achieving weight-loss and fitness goals.

Vigorous activity is effective in expending calories and achieving fitness, performance, and fat-loss goals.


Chapter 18


Caloric Cost for Walking, Caloric Cost for Walking, Jogging, and RunningJogging, and Running


Chapter 18


Estimated Energy Expenditure Estimated Energy Expenditure During ExerciseDuring Exercise


Chapter 18


Diet, Exercise, and Weight Diet, Exercise, and Weight ControlControl

• Energy and nutrient balance is more easily achieved on a low-fat diet

• Exercise increases the chance that energy balance will be achieved

• Exercise promotes health-related benefits– Increased fitness, HDL cholesterol, fibrinolysis


Chapter 18



Participation in regular physical activity achieves a wide variety of health-related goals (e.g., increased cardiorespiratory fitness, HDL cholesterol, and fibrinolysis), and increases the chance that energy balance will be achieved.


body composition and nutrition for health

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