Transcript Chapter 18 Body Composition and Nutrition for Health

Chapter 18
Body Composition and
Nutrition for Health
EXERCISE PHYSIOLOGY
Theory and Application to Fitness and Performance,
6th edition
Scott K.Presentation
Powersrevised
& Edward
T.
Howley
and updated by
Brian B. Parr, Ph.D.
University of South Carolina Aiken
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
Nutritional Goals
• Institute of Medicine dietary
recommendations (2002)
– 45–65% calories from carbohydrates
– 20–35% calories from fat
– 10–35% from protein
– Infants and younger children need higher
proportion of fat (25–40%)
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
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
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 2000 kcal•day-1 diet
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
Example of a Food Label
Figure 18.1
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)
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 (B6), folic acid, B-12, pantothenic acid, biotin,
• Involved in energy metabolism
– Vitamin C
• Maintenance of bone, cartilage, and connective tissue
Classes of Nutrients—
Minerals
Major minerals
Trace elements
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
Calcium
Sodium
Phosphorus
Magnesium
Sulfur
Potassium
Chloride
Iron
Iodine
Fluoride
Zinc
Selenium
Copper
Cobalt
Chromium
Manganese
Molybdenum
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
Classes of Nutrients—
Carbohydrates
• Sugars and starches
– Contain 4 kcals•gram-1
– Major energy source
• Crucial for red blood cells and neurons
• Dietary fiber
– Non-digestible
• Soluble and insoluble forms
• Recommendations
– Increase dietary fiber and complex carbohydrate
intake
– Decrease simple sugar intake
Classes of Nutrients—Fats
• Dietary fats
– Triglycerides
– Phospholipids
– Cholesterol
• Important energy source
– Contain 9 kcals•gram-1
• Recommendations
– Decrease total fat, saturated fat, and cholesterol
intake
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
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
Food Group Plans
• MyPyramid (2005)
– Revision of 1992 Food Guide Pyramid
– Includes major food groups
• Grains, vegetables, fruits, milk, and meat & beans
• How much of each category 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
MyPyramid Food Groups
Table 18.3
Food Group Plans
• Dietary Approaches to Stop Hypertension
(DASH)
– Developed to prevent hypertension and 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
The DASH Eating Plan
Table 18.4
Methods of Assessing
Overweight and Obesity
• Metropolitan Life Insurance Company’s
height/weight tables
– Original 1959 tables and 1983 update
– Relative weight (RW)
• Person’s weight divided by midpoint of medium frame
weight range
• RW of 1.00 is considered normal
• RW of 1.10 (10% above normal) is overweight
• RW of 1.20 (20% above normal) is obese
– Problems with height/weight tables
• High RW could be due to excess fat or muscle
Methods of Assessing
Overweight and Obesity
• 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
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
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)
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
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-compartment model
– Fat mass and fat-free mass
– Most commonly used method
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
495
fat % body fat = Density
- 450
– Based on age, gender, and race
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)
The Underwater Weighing
Technique
Figure 18.2
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 specific
equations
• Percent body fat calculated from body
density
Body Fatness for Health
and Fitness
• Recommended body fatness
– Males
• 10-20%
– Females
• 15-25%
• Health concerns above and below these
values
– Obesity
– Anorexia
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
Obesity
• Prevalence of overweight and obesity in U.S. adults
– 30.6% are obese (BMI ≥30)
– 65.7% 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 upper body obesity
• Waist circumference >102 cm (men) and >88
cm (women)
• Waist to hip ratio >0.95 (men) and >0.80
(women)
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
Relationship Between Fat Cell Size and Fat
Cell Number to Total Body Fat
Figure 18.3
Causes of Obesity
• Genetic factors
– Account for about 25% of the transmissible
variance for fat mass and percent body fat
• Cultural factors
– Account for about 30%
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
Physiological Set Point Model for
Control of Body Weight
Figure 18.4
Cognitive Set Point for Control of
Body Weight
Figure 18.5
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
rate of change of
rate of change of
=
of energy stores
energy intake
energy expenditure
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
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
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
Relationship Between the RQ/FQ
Ratio and Energy Balance
Figure 18.6
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
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
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
Decrease in Basal Metabolic Rate
During Semi-Starvation
Figure 18.7
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
• Not predictive of obesity
– Brown adipose tissue
• Increases heat production in response to
norepinephrine and thyroid hormones
– “Futile cycles”
• Metabolic cycles (Na+/K+ pump activity)
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
Relationship Between Body Fatness
and Nonbasal Energy Expenditure
Figure 18.8
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
Pattern of Caloric Intake for Rats
Versus the Durations of Exercise
Figure 18.9
Pattern of
Caloric
Intake Versus
Occupational
Activity
Figure 18.10
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
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
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
• Strategies for long-term weight loss
– 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
Caloric Cost for Walking,
Jogging, and Running
Table 18.8
Estimated Energy
Expenditure During
Exercise
Table 18.9
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