Energy Balance and Body Composition Chapter 8
Energy Balance Excess energy stored as fat Fat used for energy between meals Energy balance: energy in = energy out Imbalance causes weight changes Not simply fat changes Classic rule 1 pound of fat = 3500 kcalories Not exactly correct Differs with gender and weight
Measuring Food Energy Direct measure of food’s energy value Bomb calorimeter Indirect measure of energy released Oxygen consumed kCalorie calculations Figure 8-1 Bomb calorimeter
Food Intake Hunger Satiation – signal to stop eating Physiological response to nerve signals and chemical messengers Hypothalamus Influences Satiation – signal to stop eating Satiety – signal to not to start eating again
Hunger, Satiation, and Satiety Figure 8-2 Hunger, satiation, and satiety
Factors That Influence Eating Overriding hunger and satiety Stress eating External cues Time of day, availability, sight, taste of food Environmental influences Examples Cognitive influences Disordered eating
Nutrient Composition for Sustained Satiation and Satiety Protein is most satiating Low-energy density High-fiber foods High-fat foods – strong satiety signals Figure 8-3 How fat influences portion sizes
The Hypothalamus Control center for eating Integrates messages Energy intake, expenditure, and storage Gastrointestinal hormones Influence appetite control and energy balance
Energy Out Thermogenesis Total energy components Heat generation Measure of energy expended Total energy components Basal metabolism Physical activity Food consumption Adaptation
Basal Metabolism Represents about two-thirds of daily energy Metabolic activities All basic processes of life Basal metabolic rate (BMR) Variations Weight Lean tissue Resting metabolic rate (RMR)
Factors that Affect the BMR Effect on BMR Age Lean body mass diminishes with age, slowing the BMR.a Height In tall, thin people, the BMR is higher.b Growth In children, adolescents, and pregnant women, the BMR is higher. Body composition (gender) The more lean tissue, the higher the BMR (which is why males usually have a higher BMR than females). The more fat tissue, the lower the BMR. Fever Fever raises the BMR.C Stresses Stresses (including many diseases and certain drugs) raise the BMR. Environmental temperature Both heat and cold raise the BMR. Fasting/starvation Fasting/starvation lowers the BMR.d Malnutrition Malnutrition lowers the BMR. Hormones (gender) The thyroid hormone thyroxin, for example, can speed up or slow down the BMR.e Premenstrual hormones slightly raise the BMR. Smoking Nicotine increases energy expenditure. Caffeine Caffeine increases energy expenditure. Sleep BMR is lowest when sleeping. Table 8-2 Factors that affect the BMR a The BMR begins to decrease in early adulthood (after growth and development cease) at a rate of about 2 percent/decade. A reduction in voluntary activity as well brings the total decline in energy expenditure to about 5 percent/decade. b If two people weigh the same, the taller, thinner person will have the faster metabolic rate, reflecting the greater skin surface, through which heat is lost by radiation, in proportion to the body's volume (see Figure 8-5, p. 239). c Fever raises the BMR by 7 percent for each degree Fahrenheit. d Prolonged starvation reduces the total amount of metabolically active lean tissue in the body, although the decline occurs sooner and to a greater extent than body losses alone can explain. More likely, the neural and hormonal changes that accompany fasting are responsible for changes in the BMR. e The thyroid gland releases hormones that travel to the cells and influence cellular metabolism. Thyroid hormone activity can speed up or slow down the rate of metabolism by as much as 50 percent.
Physical Activity Voluntary movement of skeletal muscles Most variable component of energy expenditure Amount of energy needed Muscle mass Body weight Activity Frequency, intensity, and duration
Thermic Effect of Food Acceleration of GI tract functioning in response to food presence Releases heat Approximately 10 percent of energy intake High-protein foods versus high-fat foods Meal consumption time frame
Adaptive Thermogenesis Adapt to dramatically changing circumstances Examples Extra work done by body Amount expended is extremely variable Not included in energy requirement calculations
Components of Energy Expenditure Figure 8-4 Components of energy expenditure
Estimating Energy Requirements Gender BMR Growth Groups with adjusted energy requirements Age Changes with age Physical activity Levels of intensity for each gender Body composition and body size Height Weight
Ideal Body Weight: Criteria The criterion of fashion Perceived body image and actual body size Damaging behaviors Social standards for “ideal” Subjective Little in common with health The criterion of health Enough fat to meet basic needs Not so much to incur health risks
Tips for Accepting a Healthy Body Weight • Value yourself and others for human attributes other than body weight. Realize that prejudging people by weight is as harmful as prejudging them by race, religion, or gender. • Use positive, nonjudgmental descriptions of your body. • Accept positive comments from others. • Focus on your whole self including your intelligence, social grace, and professional and scholastic achievements. • Accept that no magic diet exists. • Stop dieting to lose weight. Adopt a lifestyle of healthy eating and physical activity permanently. • Follow the USDA Food Patterns. Never restrict food intake below the minimum levels that meet nutrient needs. • Become physically active, not because it will help you get thin but because it will make you feel good and improve your health. • Seek support from loved ones. Tell them of your plan for a healthy life in the body you have been given. • Seek professional counseling, not from a weight-loss counselor, but from someone who can help you make gains in self-esteem without weight as the primary focus. • Appreciate body weight for its influence on health, not appearance Table 8-5 Tips for accepting a healthy body weight
Body Mass Index (BMI) Measure of relative weight for height BMI= weight (kg) height m 2 Health-related classifications Healthy weight: BMI = 18.5 to 24.9 Other classifications Not a measure of body composition Muscular athletes Impact of ethnicity
BMI Table Table 8-6 BMI table Under-weight (<18.5) Healthy Weight Under-weight (<18.5) Healthy Weight (18.5-24.9) Overweight (25-29.9) Obese (≥ 30) 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 Height Body weight (pounds) 4"10" 86 91 96 100 105 110 115 119 124 129 134 138 143 148 153 158 162 167 172 177 181 186 191 4'11" 89 94 99 104 109 114 128 133 163 168 173 178 183 188 193 198 5'0" 92 97 102 107 112 118 123 174 179 184 189 194 199 204 5'1" 95 106 111 116 122 127 132 137 164 169 180 185 190 195 201 206 211 5'2" 98 120 126 131 136 142 147 175 196 202 207 213 218 5'3" 113 130 135 141 146 152 197 203 208 214 220 225 5'4" 140 145 151 157 192 209 215 221 227 232 5'5" 108 144 150 156 210 216 222 228 234 240 5'6" 155 161 223 229 235 241 247 5'7" 121 159 166 217 230 236 242 249 255 5'8" 125 171 243 256 262 5'9" 149 176 182 250 257 263 270 5'10" 139 160 264 271 278 5'11" 165 200 265 272 279 286 6'0" 154 258 287 294 6'1" 212 219 280 288 295 302 6'2" 233 303 311 6'3" 224 248 319 6'4" 205 238 246 254 304 312 320 328 6'5" 244 252 261 269 277 336 6'6" 259 267 276 284 293 310 345 Table 8-6 BMI table
BMI and Body Shapes Figure 8-6 BMI and body shapes
Distribution of Body Weights in US Adults Figure 8-7 Distribution of body weights in US adults
Body Fat and Its Distribution Important information for disease risk How much of weight is fat? Where is fat located? Ideal amount of body fat depends on person Age (yr) Ideal (Healthy weight, average fitness) Actual (US average) Male 20-39 18-21% 26% 40-59 22-25% 29% 60+ 24-27% 31% Female 23-26% 38% 28-32% 41% 31-34% 42% Table 8-8 Percent body fat SOURCE: L. G. Borrud and coauthors. Body composition data for individuals 8 years of age and older: US population, 1999-2004, Vital and Health Statistics 11 (2010): 1-87; ACSM's Health-Related Physical Fitness Assessment Manual, 2nd ed. (Baltimore, M.D.: Lippincott Williams & Wilkins, 2008), p. 59.
Central Obesity Needing less body fat Needing more body fat Some athletes Needing more body fat Example groups Fat distribution Visceral fat Central obesity Subcutaneous fat Figure 8-8 A central obesity
“Apple” and “Pear” Body Shapes Compared Figure 8-9 “Apple” and “pear” body shapes compared
Waist Circumference Indicator of fat distribution and central obesity Women: greater than 35 inches Men: greater than 40 inches Waist-to-hip ratio Other body composition measurement techniques More precise measures
Common Methods Used to Assess Body Fat Figure 8-10 Common methods used to assess body fat
Health Risks Associated with Body Weight and Body Fat Body weight and fat distribution correlate with disease risk and life expectancy Correlations are not causes Risks associated with being underweight Fighting against wasting diseases Menstrual irregularities and infertility Osteoporosis and bone fractures
BMI and Mortality Figure 8-11 BMI and mortality
Risks Associated With Being Overweight Obesity is a designated disease Health risks More likely to be disabled in later years Costs Medical costs Lost productivity Lives
Specific Disease Risks Cardiovascular disease Elevated blood cholesterol and hypertension Central obesity Diabetes – type II Weight gains and body weight Cancer Risk of some cancers increases with body weight Relationships not fully understood
Inflammation and the Metabolic Syndrome Change in body’s metabolism Cluster of symptoms Fat accumulation Inflammation Elevated blood lipids Promote inflammation Fit and fat versus sedentary and slim Fitness offers many health benefits
Eating Disorders Highlight 8
Eating Disorders, continued Three disorders Anorexia nervosa Bulimia nervosa Binge eating disorder Prevalence of various eating disorders Causes Multiple factors Athletes and eating disorders
Female Athlete Triad Disordered eating Amenorrhea Osteoporosis Unsuitable weight standards Body composition differences Risk factors for eating disorders in athletes Amenorrhea Characteristics Osteoporosis Stress fractures
The Female Athlete Triad Illustrated Figure H8-1 The female athlete triad
Other Dangerous Practices of Athletes Muscle dysmorphia Characteristic behaviors Similarities to others with distorted body images Food deprivation and dehydration practices Impair physical performance Reduce muscle strength Decrease anaerobic power Reduce endurance capacity
Tips for Combating Eating Disorders General Guidelines • Never restrict food amounts to below those suggested for adequacy by the USDA Food Patterns (see Table 2-2 on p. 44). • Eat frequently. Include healthy snacks between meals. The person who eats frequently never gets so hungry as to allow hunger to dictate food choices. • If not at a healthy weight, establish a reasonable weight goal based on a healthy body composition. • Allow a reasonable time to achieve the goal. A reasonable loss of excess fat can be achieved at the rate of about 10 percent of body weight in 6 months. • Establish a weight-maintenance support group with people who share interests. Specific Guidelines for Athletes and Dancers • Replace weight-based goals with performance-based goals. • Restrict weight-loss activities to the off-season. • Remember that eating disorders impair physical performance. Seek professional help in obtaining treatment if needed. • Focus on proper nutrition as an important facet of your training, as important as proper technique. Table H8-1 Tips for combating eating disorders
Anorexia Nervosa Distorted body image Malnutrition Denial Central to diagnosis Cannot be self-diagnosed Malnutrition Impacts brain function and judgment Causes lethargy, confusion, and delirium Denial Levels are high among anorexics
Characteristics of Anorexia Nervosa Need for self-control Impact on body Growth ceases and normal development falters Changes in heart size and strength Mineral imbalance Death can occur from multiple organ system failure
Treatment of Anorexia Nervosa Multidisciplinary approach Food and weight issues Relationship issues Treatment involves family members Different approaches for low, medium, and high risk patients High mortality rate among psychiatric disorders
Bulimia Nervosa Distinct and more prevalent than anorexia nervosa True incidence difficult to establish Secretive nature Not as physically apparent Common background characteristics of bulimics
Characteristics of Bulimia Nervosa Binge-purge cycle Lack of control Consume food for emotional comfort Cannot stop Done in secret Purge Cathartic Emetic Shame and guilt
The Vicious Cycle of Restrictive Dieting and Binge Eating Figure H8-2 The vicious cycle of restrictive dieting and binge eating
Negative self-perceptions Restrictive dieting Purging Binge eating Figure H8-2 The Vicious Cycle of Restrictive Dieting and Binge Eating Binge eating Stepped Art
Effects of Bulimia Nervosa Physical consequences of binge-purge cycle Subclinical malnutrition Effects Physical effects Tooth erosion, red eyes, and calloused hands High rates of clinical depression and substance abuse
Treatment of Bulimia Nervosa Discontinuing purging and restrictive diet habits Learn to eat three meals a day Plus snacks Treatment team Length of recovery Overlap between anorexia nervosa and bulimia nervosa
Diet Strategies for Combating Bulimia Nervosa Planning Principles • Plan meals and snacks; record plans in a food diary prior to eating. • Plan meals and snacks that require eating at the table and using utensils. • Refrain from finger foods. • Refrain from "dieting" or skipping meals. Nutrition Principles • Eat a well-balanced diet and regularly timed meals consisting of a variety of foods. • Include raw vegetables, salad, or raw fruit at meals to prolong eating times. • Choose whole-grain, high-fiber breads, pasta, rice, and cereals to increase bulk. • Consume adequate fluid, particularly water. Other Tips • Choose foods that provide protein and fat for satiety and bulky, fiber-rich carbohydrates for immediate feelings of fullness. • Try including soups and other water-rich foods for satiety. • Choose portions that meet the definition of "a serving" according to the USDA Food Patterns (pp. 42-43). • For convenience (and to reduce temptation) select foods that naturally divide into portions. Select one potato, rather than rice or pasta that can be overloaded onto the plate; purchase yogurt and cottage cheese in individual containers; look for small packages of precut steak or chicken; choose frozen dinners with measured portions. • Include 30 minutes of physical activity every day—exercise may be an important tool in defeating bulimia. Table H8-2 Diet strategies for combating bulimia nervosa
Binge-Eating Disorder Periodic binging Typically no purging Contrast with bulimia nervosa Similarities to bulimia nervosa Feelings Differences between obese binge eaters and obese people who do not binge Behavioral disorder responsive to treatment
Eating Disorders in Society Society plays central role in eating disorders Known only in developed nations More prevalent as wealth increases Food becomes plentiful Body dissatisfaction Incidence in young people Increased steadily since the 1950s