Energy Balance and Body Composition Lancelot McLean, PhD. lmclean@llu Energy Balance and Body Composition Lancelot McLean, PhD. lmclean@llu.edu

Energy Balance Excess energy is stored as fat Fat is used for energy between meals Energy balance: energy in = energy out A shift in balance causes weight changes 1 pound of fat = 3500 kcalories For each 3500 kcalories eaten in excess, 1lb fat gain Body fat is about 87% fat, some protein and water

Defining Healthy Body Weight How much should a person weigh? Body Mass Index (BMI) BMI = weight (kg) height (m)2 Healthy weight: BMI = 18.5 to 24.9 Not a measure of body composition A muscular athlete may be classified as overweight by BMI standards and not be “overfat”. Arnold Schwarzenegger won Mr. Olympia with BMI of 31

Defining Healthy Body Weight

Body Fat and Its Distribution Two important information for disease risk missing from weight only How much of weight is fat? Where is fat located?

Body Fat and Its Distribution How much of body weight should be FAT? General disease risk levels Young men: 22%; Men over 40: 25% Young women: 32%; Women over 40: 35%

Body Fat and Its Distribution Fat distribution Visceral fat Stored around the organs of the abdomen Upper body fat / Central Obesity Associated with increased risk of heart disease, stroke, diabetes, hypertension, and some types of cancer Most common in men and to a lesser extent postmenopausal women Subcutaneous fat Stored around hips and thighs Lower body fat Mostly common in women during reproductive years Seems relatively harmless

Body Fat and Its Distribution

Body Fat and Its Distribution

Body Fat and Its Distribution Waist circumference Good indicator of fat distribution & central obesity Women: greater than 35 inches Men: greater than 40 inches High risk of diabetes and cardiovascular disease Waist-to-hip ratio Used by some researchers Does not provide additional information

Health Risks Associated with Body Weight & Body Fat

Health Risks Associated with Body Weight & Body Fat Cardiovascular disease Elevated blood cholesterol & hypertension Diabetes – type II Central obesity Central body fat cells appear to be larger and more insulin resistant than lower body fat cells Cancer Relationship is not fully understood

Overweight and Obesity Major health problem in the U.S. 66% of US adults overweight or obese Growing concern worldwide Prevalence continues to increase Women, Poor, African Americans, and Hispanics Children 33% of US children and adolescents ages 2-19 years overweight or obese BMI of 25 or greater Epidemic is worldwide Not merely among industrialized countries > 300 million adults, 155 million children worldwide

Overweight and Obesity

Fat Cell Development Occurs when energy in exceeds energy out Stored in fat cells of adipose tissue Fat size and number Obese individuals have larger and more fat cells than healthy weight individuals Expand as they accumulate more triglycerides then proliferate more Energy out exceeds energy in Fat cell size decreases; no change in number People with extra fat cells can regain lost weight rapidly Prevention of obesity is critical during growing years when fat cells proliferate Ongoing research on how to induce fat cell death to decrease number

Caloric restriction slows aging and extends life of several species, including some mammals

Fat Cell Development

Fat Cell Metabolism Lipoprotein lipase (LPL) activity Removes triglycerides from blood for storage in adipose tissue and muscle cells Obese people have more LPL activity in adipose tissue than lean people Making fat storage efficient Activity differs in varying body regions Women Breast, hips, thighs Men Abdomen

Fat Cell Metabolism Rate of fat breakdown slower in women than men After weight loss lipoprotein lipase (LPL) activity increase Making regain of weight relatively easy After weight loss fat oxidation is not as efficient Body tries to restore the weight you previously had

Causes of Overweight & Obesity Genetics Genetics may determine predisposition to obesity Adopted children more similar in weight to biological parents Identical twins twice as likely to weigh the same However lifestyle can alter the outcome Proper diet and exercise Researchers have identified an obesity gene, called ob Expressed primarily in the adipose tissue Codes for the protein LEPTIN

Causes of Overweight & Obesity LEPTIN Acts as a hormone Leptin from adipose tissue promotes negative energy balance Suppressing appetite Increasing energy expenditure Leptin from stomach is released in response to food presence

Causes of Overweight & Obesity Mice with and without Leptin With Leptin Without Leptin

Causes of Overweight & Obesity Leptin deficiency Genetic deficiency of leptin or genetic mutation of its receptor Rare But has been identified in human beings Constantly hungry and eat considerable more than peers With daily leptin injections they lose a substantial amount of weight However vey few obese people have a leptin deficiency In fact leptin levels rise with increasing BMI to try and diminish appetite, but to no avail Due to “leptin resistance”

Causes of Overweight & Obesity Adiponectin Lean people have higher amounts Inhibits inflammation and protects against insulin resistance and cardiovascular disease Researchers trying to find ways to raise adiponectin levels in obese individuals so as to decrease disease risks

Eating Disorders Anorexia nervosa Bulimia nervosa Eating disorder characterized by refusal to maintain a normal body weight Intense fear of gaining weight or becoming obese Disturbance of body image resulting in a feeling of being fat or having fat in certain areas even when extremely emaciated Bulimia nervosa Eating disorder involving episodic binge eating followed by behaviors designed to prevent weight gain, including purging, fasting and excessive exercise Binge eating disorder Eating disorder characterized by binge eating, rarely purging and exert less restraint than bulimics during times of dieting