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
– 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
 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
Requirements

Gender

 Tends to decrease
with time
 BMR

Growth
 Groups with
adjusted energy
requirements
 Infants, children,
adolescents,
pregnant and
lactating women
Age

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