Chapter
8
Energy Balance, Body
Composition, and
Weight Management
Energy Equilibrium
• Energy Intake refers to the amount of fuel
(calories) you take in through consumption of
carbohydrate, protein, fat and alcohol.
• Energy Output is the amount you expend –
primarily for basic body functions, physical
activity, and the processing of food.
• Energy equilibrium is demonstrated in people
who maintain a relatively constant weight.
Positive Energy Balance
• Positive energy balance – when you take in
more energy than your body needs.
– Surplus is stored as fat (long-term) and glycogen
(short-term).
– Pregnant women and growing children need a
positive energy balance.
– A positive energy balance due to overeating and
inactivity leads to weight gain.
Negative Energy Balance
• Negative energy balance – when you take in
less energy than your body needs.
– Illness.
– Intentional change for weight loss.
– The body uses stores of glycogen and fat (protein
as well with extreme deficits).
Energy Equilibrium
• Energy equilibrium – when the energy intake
is about equal to the energy output.
• Body weight change reflects overall energy
balance.
Energy Balance
Bomb Calorimeter
• We can measure the energy content of a food
with a bomb calorimeter.
Bomb Calorimeter
• Food is completely burned inside a sealed
chamber and sensors measure the amount of
heat produced by combustion.
• The human body does not completely digest
all food and is unable to oxidize nitrogen.
Therefore, we adjust the energy content
downward to reflect this.
Energy In
• Regulation of intake
– Hunger
• Prompts eating; physiological
desire
– Satiation
• Signals to stop eating
– Satiety
• Lack of hunger
– Appetite
• Psychological desire
Hunger
• The internal, physiological drive to find and
consume food. Unlike appetite, hunger is
usually experienced as a negative sensation,
often manifesting as an uneasy and painful
sensation.
Appetite
• Appetite is a psychological desire to eat that is
related to the pleasant sensations often
associated with food.
• Appetite can trigger a desire for food, even
when you are not truly hungry.
• Anorexia is a decreased desire to eat food.
• Polyphagia (hyperphagia) is an increased
desire to eat food.
Satiation / Satiety
• Satiation is a feeling of satisfaction and
fullness that terminates a meal.
• Satiety is a feeling of satisfaction or fullness
following a meal that quells the desire for
food. It delays subsequent intake.
Energy In: Regulatory Factors
Energy Out: Fuel Uses
• Major components of energy expenditure
– Resting energy expenditure (REE)
• Energy for basic body functions
• Affected by body size, composition, age, gender
– Physical activity
• Highly variable
• Affected by body size, fitness level,
type of activity
– Thermic effect of food (TEF)
• Energy to digest, absorb,
metabolize food
Measuring Energy Expenditure
• Brief history
• Direct vs.
indirect
calorimetry
• Doubly labeled
water
Estimating Energy Expenditure
• EER: Estimated Energy Requirement
– Predicts total energy expenditure (TEE)
– Equations for males and females
• Factors for age, weight, height, physical activity
Body Composition: Understanding
Fatness and Weight
• Assessing body weight
– Height–weight tables
– Body mass index (BMI)
• Weight (kg)  height2 (m)
• Assessing body fatness
• Body fat distribution
– Waist circumference
Body Mass Index
• What are the health risks associated with being
overweight?
When Energy Balance Goes Awry
• Early theories of weight regulation
– Fat cell theory
– Set point theory
• Influences on weight gain and obesity
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Heredity and genetic factors
Sociocultural influences
Age and lifestyle factors
Gender and ethnicity
Socioeconomic factors
Psychological factors
Weight Management
• Perception of weight
• Setting realistic goals
• Weight-management lifestyle
– Diet and eating habits
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Reduce total calories
Reduce fat calories
Increase complex carbohydrates
Improve eating habits
– Increase physical activity
– Stress management
– Self-acceptance
Weight Management
• Weight-management approaches
– Self-help books and manuals
• Watch for signs of a fad diet
– Self-help groups
– Commercial programs
– Professional counselors
– Prescription drugs
– OTC drugs and dietary supplements
Weight Management
• Weightmanagement
approaches
– Surgery
Underweight
• Definition
– BMI < 18.5 kg/m2
• Causes
– Illness
– Eating disorders
– Metabolic factors
• Weight-gain strategies
– Small, frequent meals
– Fluids between meals
– High-calorie foods and beverages
Healthy Weight Management
• Healthy weight management means focusing
on metabolic fitness—healthy levels of blood
lipids and blood pressure—rather than on
achieving a specific weight.
• Permanent healthy behaviors are necessary
for a long-term weight-management lifestyle.
Why Do We Have Hunger Pangs?
• When the stomach has been without food for at
least three hours, intense stomach contractions
begin, sometimes lasting two to three minutes.
• Healthy young people have the strongest
contractions, due to good muscle tone in the GI tract.
• After 12 to 24 hours, contractions of an empty
stomach can cause painful hunger pangs.
Overweight and Obesity
• Worldwide, the number of overweight or
obese people has increased markedly in
recent years. The rising rates among children
are especially disturbing.
• At the same time, more people are engaging
in weight-control efforts and starting to do so
at younger ages.
Emotional Factors
• Many people use food to cope with stress and
negative emotions. Eating can provide a powerful
distraction from loneliness, anger, boredom, anxiety,
shame, sadness, and inadequacy.
• To combat low moods, low energy levels, and low
self-esteem, people often turn to the refrigerator.
When we use food and eating to cope with our
emotions, binge eating or other disturbed eating
patterns can develop.
Weight Cycling
• Weight cycling is a pattern of losing and regaining
weight, over and over again. You might expect this
behavior to be harmful, perhaps harder on the body
than overweight itself.
• However, research shows that the potential benefits
of weight loss for obese individuals outweigh the
potential risks of weight cycling.
Balancing Energy Sources
• Balancing energy sources and controlling portion
sizes can help reduce overall energy consumption.
Reducing fat intake is a major step toward lowering
calorie intake. Fiber-rich foods provide a feeling of
fullness that can help prevent overeating.
• When planning a diet, aim for a caloric intake of 20
to 35 percent fat, 10 to 35 percent protein, and 45 to
65 percent carbohydrate.
The Built Environment
• Our immediate surroundings influence our behaviors, and
researchers have begun to link aspects of the built
environment with obesity. The built environment, which can
be defined as “human formed, developed, or structured
areas,” includes buildings, roads, parks, and transportation
systems.
• People who live in neighborhoods with sidewalks and safe
streets are more physically active. But when neighborhoods
have low “walkability” or are considered unsafe, BMIs tend to
be higher.
Meal Replacements
• Some people turn to meal replacements— shakes
and bars, for example—to help lose weight. Meal
replacements are convenient, often contain added
vitamins and minerals, and reduce the choices and
temptations available at mealtime.
• When compared with traditional, reduced-calorie
diet programs, people using meal replacements lost
slightly more weight and were less likely to stop the
program.
Weight-Management Strategies
• Books, Internet resources, and commercial programs can help
some individuals lose weight. However, consumers should
always proceed with caution before spending money. Drugs
have potential side effects and must be used with caution and
medical supervision.
• For those who are extremely obese, surgical intervention is an
aggressive, last-resort approach to weight management.
Liposuction removes fat cells from specific parts of the body
but is not considered an effective approach to weight control.
ADA Position on Weight Management
• It is the position of the American Dietetic
Association that successful weight
management to improve overall health for
adults requires a lifelong commitment to
healthful lifestyle behaviors emphasizing
sustainable and enjoyable eating practices and
daily physical activity.