Energy Balance and Weight Management Chapter 7

Overweight and Obesity Major health problem in the U.S. Growing concern worldwide Prevalence increasing among all socioeconomic groups 2/3 of adults Children: 1/3, ages 2-19 Overweight: BMI of 25-29 Obese: BMI of 30 or greater Epidemic is worldwide Not merely among industrialized countries

This Took 20 Years!

What’s Going On? Increased Intake Decreased Energy Expenditure Portion Distortion Appetite versus Hunger Decreased Energy Expenditure Changes in recreational activities Modern technology

Weight Management Terms Energy balance occurs when energy consumed equals energy expenditure. Energy is measured in kilocalories (kcal, kcalories) or kilojoules (kjoules, kJ). A kcalorie is a measure of the amount of energy that is supplied to or expended by the body. Body Mass Index (BMI) is a mathematical comparison of weight to height Overweight is being too heavy for one’s height or having a BMI of 25–29. Obesity is characterized by excess body fat or a BMI over 30.

Energy In: Food Composition Direct measure of food’s energy value Bomb calorimeter kCalorie calculations Not an exact science when it comes to how food behaves the body!

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 Not simply fat changes When weight loss occurs, body energy stores are used When weight gain occurs, body energy stores are built

Energy Balance: Ins vs. Outs

Using Nutrients for Energy (ATP)

Storing Energy in Adipose Tissue

Fat Cell Development Energy in exceeds energy out Body fat Stored in fat cells of adipose tissue Body fat Number and size of fat cells Periods in life when fat cell numbers increase: puberty and excess intake Cell proliferation Energy out exceeds energy in Fat cell size decreases; no change in number

During growth, fat cells increase in number. When energy intake exceeds expenditure, fat cells increase in size. When fat cells have enlarged and energy intake continues to exceed energy expenditure, fat cells increase in number again. With fat loss, the size of the fat cells shrinks but not the number. Figure 9.2: Fat Cell Development. Fat cells are capable of increasing their size by 20-fold and their number by several thousandfold.

Estimating Energy Requirements Gender BMR Growth Groups with adjusted energy requirements Infants, children, adolescents, pregnant and lactating women Age Tends to decrease with time Physical activity Kcal burned in moment vs. afterburn Body composition & body size Height Weight

Estimated Energy Requirement

Physical Activity Factor (PA)

Estimating PA Intensity

Calculating Body Mass Index Body mass index (BMI) Relative weight for height BMI = weight (kg) height (m)2 Health-related classifications Underweight: <18.5 Healthy weight: 18.5 to 24.9 Overweight: 25-29.9 Obese: 30 or above Not a measure of body composition!

Assessing Body Composition Bioelectric impedance analysis Skinfold thickness Underwater weighing Dilution methods Radiologic methods

Measurement of Body Composition

Excess Body Fat and Disease Risk

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 individual Healthy ranges Men: 13-21% Women: 23-31% Obese individuals: up to 70% body fat

Body Fat and Its Distribution Weight alone doesn’t tell the whole story! Waist circumference Indicator of fat distribution & central obesity Women: risk at greater than 35 inches Men: risk at greater than 40 inches Waist-to-hip ratio: Women: risk at greater than 0.8 Men: risk at greater than 0.9

Fat Distribution: Visceral Fat

Apple- vs. Pear-Shaped Bodies

Health Risks Associated with Body Weight & Body Fat Risks associated with being overweight Obesity is a designated disease Health risks Heart disease, hypertension, diabetes, sleep apnea, osteoarthritis, some cancers, gallbladder disease, kidney stones, infertility, complications in pregnancy and surgery More likely to be disabled in later years Costs Money: health care costs as much or more than that of smoking Lives: ~300,000/year from related diseases

Estimating Disease Risk

Who would benefit from weight loss?

Defining Healthy Body Weight What is ideal? Not appearance-based Perceived body image and actual body size can be quite different Dissonance can lead to damaging behaviors Subjectivity of ideal body type Shifts from one culture to another, from one decade to the next Little in common with health

Body Fat and Its Distribution

Health Risks Associated with Body Weight & Body Fat Body weight and fat distribution correlate with disease risk and life expectancy Correlations are not causes Overweight does not equal unhealthy Risks associated with being underweight Fighting against wasting diseases Menstrual irregularities and infertility Osteoporosis and bone fractures

Health Risks Associated with Body Weight & Body Fat