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Scott K. Powers • Edward T. Howley
Theory and Application to Fitness and Performance
SEVENTH EDITION
Chapter
Body Composition and
Nutrition for Health
Presentation prepared by:
Brian B. Parr, Ph.D.
University of South Carolina Aiken
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Chapter 18
Objectives
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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Chapter 18
Objectives
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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Chapter 18
Objectives
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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Chapter 18
Objectives
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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Chapter 18
Objectives
14.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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Chapter 18
Objectives
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,
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Chapter 18
Objectives
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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Chapter 18
Outline
 Nutritional Goals
 Standards of
Nutrition
 Classes of
Nutrients
Water
Vitamins
Minerals
Carbohydrates
Fats
Protein
 Body Composition  Obesity and
Weight Control
Methods of Assessing
Overweight and
Obesity
Methods of Measuring
Body Composition
Two-Component
System of Body
Composition
Body Fatness for
Health and Fitness
Obesity
 Diet, Exercise,
and Weight
Control
Energy and Nutrient
Balance
Diet and Weight
Control
Energy Expenditure
and Weight Control
 Meeting the
Guidelines and
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Chapter 18
Nutritional Goals
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
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Chapter 18
Nutritional 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
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Chapter 18
Nutritional Goals
Dietary Guidelines for
Americans (1980)
• Did not provide specific quantities to
achieve for fat, cholesterol, salt, and
carbohydrates
• More general statements for good health
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Chapter 18
Nutritional Goals
Institute of Medicine Dietary
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
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Chapter 18
Nutritional Goals
Dietary Guidelines for
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
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Chapter 18
Nutritional Goals
Clinical Applications 18.1
Institute 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)
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Chapter 18
Nutritional Goals
In 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.
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Chapter 18
Standards of Nutrition
Dietary Reference Intakes
(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
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Chapter 18
Standards of Nutrition
Standards 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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Chapter 18
Standards of Nutrition
Nutritional 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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Chapter 18
Standards of Nutrition
Example of a Food Label
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Figure 18.1
Chapter 18
Standards of Nutrition
In Summary
 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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Chapter 18
Classes of Nutrients
Water
• 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)
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Chapter 18
Classes of Nutrients
Vitamins
• 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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Chapter 18
Classes of Nutrients
Summary of the Fat-Soluble
Vitamins
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Chapter 18
Classes of Nutrients
Summary of the Water-Soluble
Vitamins
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Chapter 18
Classes of Nutrients
In Summary
 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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Chapter 18
Classes of Nutrients
Classes of Nutrients—Minerals
• For a summary of minerals, see
Major
minerals
Trace elements
Table
18.2
•
•
•
•
•
•
•
Calcium
Sodium
Phosphorus
Magnesium
Sulfur
Potassium
Chloride
•
•
•
•
•
•
•
•
•
•
•
•
•
Iron
Iodine
Fluoride
Zinc
Selenium
Copper
Cobalt
Chromium
Manganese
Molybdenum
Arsenic
Nickel
Vanadium
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Chapter 18
Classes of Nutrients
Minerals
• 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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Chapter 18
Classes of Nutrients
In 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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Chapter 18
Classes of Nutrients
Carbohydrates
• 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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Chapter 18
Classes of Nutrients
Carbohydrates
• 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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Chapter 18
Classes of Nutrients
Clinical Applications 18.2
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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Chapter 18
Classes of Nutrients
Fats
• 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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Chapter 18
Classes of Nutrients
Fats
• 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
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Chapter 18
Clinical Applications 18.3
Classes of Nutrients
Diet Composition and
Syndrome 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
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size
Chapter 18
Classes of Nutrients
Proteins
• 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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Chapter 18
Classes of Nutrients
In Summary
 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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Chapter 18
Classes of Nutrients
In Summary
 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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Chapter 18
Meeting the Guidelines and Achieving the Goals
Meeting the Guidelines and
Achieving 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
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Chapter 18
Meeting the Guidelines and Achieving the Goals
Food 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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Chapter 18
Meeting the Guidelines and Achieving the Goals
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
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Chapter 18
Meeting the Guidelines and Achieving the Goals
MyPyramid Food Groups
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Chapter 18
Meeting the Guidelines and Achieving the Goals
Dietary Approaches to Stop
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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Chapter 18
Meeting the Guidelines and Achieving the Goals
The DASH Eating Plan
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Chapter 18
Meeting the Guidelines and Achieving the Goals
Evaluating 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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Chapter 18
Meeting the Guidelines and Achieving the Goals
In Summary
 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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Chapter 18
Body Composition
Methods of Assessing Overweight
and 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
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Chapter 18
Body Composition
Methods of Measuring Body
Composition
• 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
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Chapter 18
Body Composition
Methods of Measuring Body
Composition
• 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
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Chapter 18
Body Composition
Methods of Measuring Body
Composition
• 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
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Chapter 18
Body Composition
Body 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
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Chapter 18
Body Composition
In Summary
 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).
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Chapter 18
Body Composition
In Summary
 Body composition assessment can be
based on four-component (mineral,
water, protein, and fat), threecomponent (body water,
protein+mineral, and fat, or body
water+protein, mineral, and fat), or twocomponent (fat-free mass and fat mass)
models. The four-component model is
the most accurate.
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Chapter 18
Body Composition
Two-Component System of
Body Composition
• 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:
495
– 450
% body fat =
Density
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Chapter 18
Body Composition
Estimating % Fat from Body
Density
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Chapter 18
Body Composition
Underwater 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)
MA
M
D=
=
V
(MA – MW)
– VR – VGI
(DW)
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Chapter 18
Body Composition
The Underwater Weighing
Technique
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Figure 18.2
Chapter 18
Body Composition
In Summary
 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).
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Chapter 18
Body Composition
In 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.
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Chapter 18
Body Composition
Skinfolds
• 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
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Chapter 18
Body Composition
Prediction of % Fat Based on Skinfolds
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Chapter 18
Body Composition
Body Fatness for Health and
Fitness
• 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
Optimal weight =
Fat-free weight
(1 – optimal % fat)
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Chapter 18
Body Composition
In Summary
 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.
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Chapter 18
Obesity
Obesity
• 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
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Chapter 18
Obesity
Obesity
• 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)
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Chapter 18
Obesity
Fat 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
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Chapter 18
Obesity
Relationship Between Fat Cell Size and Fat
Cell Number to Total Body Fat
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Figure 18.3
Chapter 18
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%
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Chapter 18
Obesity
In 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%.
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Chapter 18
Obesity
Set 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
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Chapter 18
Obesity
Physiological Set Point Model
for Control of Body Weight
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Figure 18.4
Chapter 18
Cognitive Set Point for Control of
Body Weight
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Obesity
Figure 18.5
Chapter 18
Obesity
Clinical Applications 18.4
Drugs, 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
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Chapter 18
Obesity
In Summary
 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.
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Chapter 18
Diet, Exercise, and Weight Control
Energy Balance
• Static energy balance
– Increase intake of 250 kcals•day–1 would lead to
14-pound weight gain over one year
change of
energy
energy
=
–
energy stores
intake
expenditure
• 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
rate of change of
–
energy intake
energy expenditure
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Chapter 18
Diet, Exercise, and Weight Control
In Summary
 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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Chapter 18
Diet, Exercise, and Weight Control
Nutrient 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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Chapter 18
Diet, Exercise, and Weight Control
The 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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Chapter 18
Diet, Exercise, and Weight Control
The 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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Chapter 18
Diet, Exercise, and Weight Control
Relationship Between the RQ/FQ Ratio and
Energy Balance
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Figure 18.6
Chapter 18
Diet, Exercise, and Weight Control
In Summary
 Nutrient balance exists for both protein
and carbohydrate. Excess intake is
oxidized and is not converted to fat.
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Chapter 18
Diet, Exercise, and Weight Control
Diet 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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Chapter 18
Diet, Exercise, and Weight Control
Physical 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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Chapter 18
Diet, Exercise, and Weight Control
In Summary
 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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Chapter 18
Diet, Exercise, and Weight Control
Energy 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
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Chapter 18
Diet, Exercise, and Weight Control
Decrease in Basal Metabolic
Rate During Semi-Starvation
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Figure 18.7
Chapter 18
Diet, Exercise, and Weight Control
In 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.
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Chapter 18
Diet, Exercise, and Weight Control
Energy Expenditure and Weight Control
• 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)
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Chapter 18
Diet, Exercise, and Weight Control
In Summary
 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.
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Chapter 18
Diet, Exercise, and Weight Control
Energy Expenditure and Weight
Control
• 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
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Relationship Between
Body
Diet, Exercise,
and Weight Control
Fatness and Nonbasal Energy
Expenditure
Chapter 18
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Figure 18.8
Chapter 18
Diet, Exercise, and Weight Control
Clinical Applications 18.5
A 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
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Chapter 18
Diet, Exercise, and Weight Control
Pattern of Caloric Intake for Rats
Versus the Durations of Exercise
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Figure 18.9
Chapter 18
Diet, Exercise, and Weight Control
Effect 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
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Chapter 18
Pattern of
Caloric
Intake
Versus
Occupatio
nal Activity
Diet, Exercise, and Weight Control
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Figure 18.10
Chapter 18
Diet, Exercise, and Weight Control
Exercise 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
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Chapter 18
Diet, Exercise, and Weight Control
In Summary
 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.
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Chapter 18
Diet, Exercise, and Weight Control
Exercise, Weight Loss, and Weight
Maintenance
• 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
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Chapter 18
Diet, Exercise, and Weight Control
Clinical Applications 18.6
Successful Losers—How Much Exercise Is Needed
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
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Chapter 18
Clinical Applications
18.6
Diet, Exercise, and Weight Control
Successful Losers—How Much
Exercise is Needed to Keep the
• Strategies forWeight
long-termOff?
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
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Chapter 18
Diet, Exercise, and Weight Control
In Summary
 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.
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Chapter 18
Diet, Exercise, and Weight Control
Caloric Cost for Walking,
Jogging, and Running
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Chapter 18
Diet, Exercise, and Weight Control
Estimated Energy Expenditure
During Exercise
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Chapter 18
Diet, Exercise, and Weight Control
Diet, Exercise, and Weight
Control
• 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
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Chapter 18
Diet, Exercise, and Weight Control
In Summary
 Participation in regular physical activity
achieves a wide variety of healthrelated goals (e.g., increased
cardiorespiratory fitness, HDL
cholesterol, and fibrinolysis), and
increases the chance that energy
balance will be achieved.
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