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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, 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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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
 Body Composition
 Nutritional Goals
Methods of Assessing
 Standards of Nutrition
Overweight and Obesity
 Classes of Nutrients
Methods of Measuring
Body Composition
Two-Component System
of Body Composition
Body Fatness for Health
and Fitness
Water
Vitamins
Minerals
Carbohydrates
Fats
Protein
 Obesity and Weight
Control
Obesity
 Diet, Exercise, and
Weight Control
Energy and Nutrient
Balance
Diet and Weight Control
Energy Expenditure and
Weight Control
 Meeting the Guidelines
and Achieving the
Goals
Food Group Plans
Evaluating the Diet
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Nutritional Goals
Chapter 18
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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Nutritional Goals
Chapter 18
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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Nutritional Goals
Chapter 18
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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Nutritional Goals
Chapter 18
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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Nutritional Goals
Chapter 18
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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Nutritional Goals
Chapter 18
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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Nutritional Goals
Chapter 18
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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Standards of Nutrition
Chapter 18
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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Standards of Nutrition
Chapter 18
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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Standards of Nutrition
Chapter 18
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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Classes of Nutrients
Chapter 18
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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Classes of Nutrients
Chapter 18
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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Classes of Nutrients
Chapter 18
Summary of the Fat-Soluble Vitamins
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Classes of Nutrients
Chapter 18
Summary of the Water-Soluble Vitamins
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Classes of Nutrients
Chapter 18
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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Classes of Nutrients
Chapter 18
Classes of Nutrients—Minerals
• For a summary of minerals, see Table 18.2
Major minerals
•
•
•
•
•
•
•
Calcium
Sodium
Phosphorus
Magnesium
Sulfur
Potassium
Chloride
Trace elements
•
•
•
•
•
•
•
•
•
•
•
•
•
Iron
Iodine
Fluoride
Zinc
Selenium
Copper
Cobalt
Chromium
Manganese
Molybdenum
Arsenic
Nickel
Vanadium
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Classes of Nutrients
Chapter 18
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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Classes of Nutrients
Chapter 18
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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Classes of Nutrients
Chapter 18
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 sugarcontaining foods and beverages less frequently
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Classes of Nutrients
Chapter 18
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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Classes of Nutrients
Chapter 18
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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Classes of Nutrients
Chapter 18
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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Classes of Nutrients
Chapter 18
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
– Limit intake of fat and oils high in saturated and/or
trans fatty acids
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Classes of Nutrients
Chapter 18
Clinical Applications 18.3
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
Larger fat cell size
Higher blood pressure
– Compared to low-fat, complex-carbohydrate diet
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Classes of Nutrients
Chapter 18
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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Classes of Nutrients
Chapter 18
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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Classes of Nutrients
Chapter 18
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 lowfat 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
• Consistent with most dietary recommendations
– Should help control health conditions
– Vitamin E and potassium intake may be too low
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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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Body Composition
Chapter 18
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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Body Composition
Chapter 18
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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Body Composition
Chapter 18
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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Body Composition
Chapter 18
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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Body Composition
Chapter 18
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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Body Composition
Chapter 18
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 heightweight 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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Body Composition
Chapter 18
In Summary
 Body composition assessment can be based on fourcomponent (mineral, water, protein, and fat), threecomponent (body water, protein+mineral, and fat, or
body water+protein, mineral, and fat), or two-component
(fat-free mass and fat mass) models. The fourcomponent model is the most accurate.
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Body Composition
Chapter 18
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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Body Composition
Chapter 18
Estimating % Fat from Body Density
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Body Composition
Chapter 18
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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Body Composition
Chapter 18
The Underwater Weighing Technique
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Figure 18.2
Body Composition
Chapter 18
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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Body Composition
Chapter 18
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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Body Composition
Chapter 18
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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Body Composition
Chapter 18
Prediction of % Fat Based on Skinfolds
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Body Composition
Chapter 18
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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Body Composition
Chapter 18
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 fourcomponent 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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Obesity
Chapter 18
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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Obesity
Chapter 18
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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Obesity
Chapter 18
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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Obesity
Chapter 18
Relationship Between Fat Cell Size and
Fat Cell Number to Total Body Fat
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Figure 18.3
Obesity
Chapter 18
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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Obesity
Chapter 18
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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Obesity
Chapter 18
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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Obesity
Chapter 18
Physiological Set Point Model for Control
of Body Weight
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Figure 18.4
Obesity
Chapter 18
Cognitive Set Point for Control of
Body Weight
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Figure 18.5
Obesity
Chapter 18
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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Obesity
Chapter 18
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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Diet, Exercise, and Weight Control
Chapter 18
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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Diet, Exercise, and Weight Control
Chapter 18
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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Diet, Exercise, and Weight Control
Chapter 18
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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Diet, Exercise, and Weight Control
Chapter 18
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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Diet, Exercise, and Weight Control
Chapter 18
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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Diet, Exercise, and Weight Control
Chapter 18
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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Diet, Exercise, and Weight Control
Chapter 18
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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Chapter 18
Diet, Exercise, and Weight Control
Relationship Between Body Fatness and
Nonbasal Energy Expenditure
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Figure 18.8
Diet, Exercise, and Weight Control
Chapter 18
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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Diet, Exercise, and Weight Control
Chapter 18
Pattern of
Caloric
Intake
Versus
Occupational
Activity
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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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Diet, Exercise, and Weight Control
Chapter 18
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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Diet, Exercise, and Weight Control
Chapter 18
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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Diet, Exercise, and Weight Control
Chapter 18
Clinical Applications 18.6
Successful Losers—How Much Exercise
is Needed to Keep the 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
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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 weightloss 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 health-related goals (e.g., increased
cardiorespiratory fitness, HDL cholesterol, and
fibrinolysis), and increases the chance that energy
balance will be achieved.
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Chapter 18
Study Questions
1.
Summarize the range of carbohydrate, fat, and protein
intakes recommended by the Institute of Medicine.
2.
What is the difference between an RDA standard and a Daily
Value?
3.
Is there any risk in taking fat-soluble vitamins in large
quantities? Explain.
4.
Which two minerals are believed to be inadequate in
women’s diets?
5.
Relative to coronary heart disease, why is there a major
focus on dietary fat?
6.
Generate a one-week menu using the MyPyramid website.
How do the choices compare to those in the DASH eating
plan?
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Chapter 18
Study Questions
7.
Using a height/weight table, how fat is a football player who
is 74 inches tall and weighs 235 lb?
8.
Identify and describe the following methods of measuring
body composition: isotope dilution, potassium-40,
ultrasound, bioelectric impedance analysis, dual energy xray absorptiometry, skinfold thickness, and underwater
weighing.
9.
Contrast the four-component and two-component models of
body composition assessment.
10. What is the principle of underwater weighing? Why should a
different body density equation be used for children, in
contrast to adults?
11. Given: a twenty-year-old college male, 180 lb, 28% fat. What
is his target body weight to achieve 17% fat?
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Chapter 18
Study Questions
12. In terms of the resistance to weight reduction, contrast
obesity due to hypertrophy with obesity due to hyperplasia
of fat cells.
13. Is obesity more related to genetics or the environment?
14. If a person consumes 120 kcal per day in excess of need,
what weight gain does the static energy balance equation
predict compared to the dynamic energy balance equation?
15. What does nutrient balance mean and how is the ratio of the
RQ to FQ used to determine nutrient balance?
16. Contrast a physiological set point with a behavioral set point
related to obesity.
17. What happens to the BMR when a person goes on a lowcalorie diet?
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Chapter 18
Study Questions
18. What recommendations would you give about the use of diet
alone versus a combination of diet and exercise?
19. What is thermogenesis and how might it be related to weight
gain?
20. What is the effect of exercise on appetite and body
composition?
21. What exercise recommendation is appropriate and
consistent with achieving caloric-expenditure and fat-loss
goals for someone who is sedentary and overweight?
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