Energy Balance and Energy Balance and Weight ManagementWeight Management

Chapter 7

Overweight and ObesityOverweight 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!This Took 20 Years!

What’s Going On? Increased Intake

– 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 Energy In: Food CompositionComposition

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 BalanceEnergy 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

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.

Estimating Energy Estimating Energy RequirementsRequirements

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 Calculating Body Mass IndexIndex

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 Body Fat and Its DistributionDistribution

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 Body Fat and Its DistributionDistribution

Weight alone doesn’t tell the whole story! Waist circumference

Indicator of fat distribution & central obesityWomen: risk at greater than 35 inchesMen: 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 Distribution: Visceral FatFat

Apple- vs. Pear-Shaped Apple- vs. Pear-Shaped BodiesBodies

Health Risks Associated Health Risks Associated with Body Weight & Body with Body Weight & Body FatFat

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?

DefininDefining g Healthy Healthy Body Body WeightWeight 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 Body Fat and Its DistributionDistribution

Health Risks Associated Health Risks Associated with Body Weight & Body with Body Weight & Body FatFat

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 Health Risks Associated with Body Weight & Body with Body Weight & Body FatFat