Energy Balance

“State in which energy intake, in the form of food and /or alcohol, matches the energy expended, primarily through basal metabolism and physical activity”

Positive energy balance

Energy intake > energy expended

Results in weight gain

Negative energy balance

Energy intake < energy expended

Results in weight loss

Energy Balance

Estimating Kcal Content in Food

Bomb calorimeter

Burns food inside a chamber surrounded by water

Heat is given off as food is burned

The increase in water temperature indicates the amount of energy in the food

Fat Storage

FAT

Most fat is stored directly into adipose tissue

Body has unlimited ability to store fat (as fat)

CARBOHYDRATES

Limited CHO can be stored as glycogen

Most CHO is used as a energy source

Excessive CHO will be synthesized into fat (for storage)

Protein and Fat Storage

Protein is primarily used for tissue synthesis

Adults generally consume more protein than needed for tissue synthesis

Excess protein is used as a energy source

Some protein will be synthesized into fat (for storage)

Macronutrients and Fat Storage

Body prefers to use CHO as energy source

Only excess intake of CHO and protein will be turned into fat

Fat will remain as fat for storage

Physical activity encourages the burning of dietary fat

Beta-oxidation

Most endurance athletes burn fatty acids for energy

glycogen is used also

Energy In Vs. Energy Out

NEAT

Basal Metabolism

Dietary Intake Physical Activity

Thermic Effect of food

Basal Metabolism

The minimum energy expended to keep a resting, awake body alive

~60-70% of the total energy needs

Includes energy needed for maintaining a heartbeat, respiration, body temperature

Amount of energy needed varies between individuals

Influences On Basal Metabolism

Body surface area (weight, height)

Gender

Body temperature

Thyroid hormone

Age (2% decline/decade past 30)

Kcal intake

Pregnancy

Use of caffeine and tobacco

Measurement of Body’s Energy NeedsDirect calorimetry

Measures heat output from the body using an insulated chamber

Expensive and complex

Indirect calorimetry

Measures the amount of oxygen a person uses

A relationship exists between the body’s production of energy and oxygen

Physical Activity

Increases energy expenditure beyond BMR

Varies widely among individuals

More activity, more energy burned

Lack of activity is the major cause of obesity

Thermic Effect of Food (TEF)

Energy used to digest, absorb, and metabolize food nutrients

“Sales tax” of total energy consumed

~5-10% above the total energy consumed

TEF is higher for CHO and protein than fat

Less energy is used to transfer dietary fat into adipose stores

Harris-Benedict Equation

Estimates resting energy needs

Considers height, weight, age, and gender

For men:

66.5 + 13.8x(kg) + 5x(cm) - 6.8x(age in yr.)

For women:

655.1 + 9.6x(kg) + 1.8x(cm) - 4.7x(age in yr.)

Sample Calculations

Man: 21 yr., 5’10” (171 cm), 155# (70 kg)

66.5 + 13.8x(70kg) + 5x(171cm) - 6.8x(21) = 1745 kcal/day

Woman: 21 yr., 5’10” (171 cm), 155# (70kg)

655.1 + 9.6x(70kg) + 1.8x(171cm) - 4.7x(21)= 1536 kcal/day

Why Do You Eat?

Hunger

Physiological (internal) drive to eat

Controlled by internal body

Appetite

Psychological (external) drive to eat

Often in the absence of hunger

e.g., seeing/smelling fresh baked chocolate chip cookies

Satiety Regulator

The hypothalamusWhen feeding cells are stimulated, they signal

you to eatWhen satiety cells are stimulated, they signal you

to stop eatingSympathetic nervous system

When activity increases, it signals you to stop eating

When activity decreases, it signals you to eat

Influences of Satiety

Influences of Satiety

Influenced By Body Composition

Leptin A hormone produced by the adipose tissue

Increases with larger fat mass (and decrease desire to eat)

Decreases with lower fat mass (and enhance desire to eat)

Acts to decrease activity of neuropeptide Y

Neuropeoptide YIncreases food intake

Reduces energy expenditure

Hormonal Influence

EndorphinsNatural body tranquilizer that can prompt you to eat

CCKAlong with gastrointestinal distention, decreases hunger

(and desire to eat)

SerotoninNeurotransmitter that is released as a result of CHO intake

High levels appear to decrease desire to eat CHO and induce calmness

Hormonal Influence

Nutrient receptors

In small intestine

Elicit feeling of satiety

Communicate with the brain via nerves

Inform brain of the presence of nutrients in the small intestine

Feeling of satiety with the infusing of CHO or fats in the small intestine

Nutrients Influence

Presence of energy yielding nutrient registers satiety in the brain

Apolipoprotein A-IV on the chylomicrons signals satiety in the brain

Absence of these nutrients will signal hunger

What is a Healthy Body Weight?

Based on how you feel, weight history, fat distribution, family history of obesity-related disease, current health status, and lifestyle

Current height/weight standards only provide guides

Body Mass Index (BMI)

The preferred weight-for-height standard

Calculation:

Body wt (in kg) OR Body wt (in lbs) x 703.1

[Ht (in m)]2 [Ht (in inches)]2

Health risks increase when BMI is > 25

Estimation of Healthy Weight

For men:

106 pounds for the first 5 feet

add 6 pounds per each inch over five feet

A man who is 5’10” should weigh 166 lbs.

For women:

100 pounds for the first 5 feet

add 5 pounds per each inch over five feet

A women who is 5’10” should weigh 150 lbs.

Obesity

Excessive amount of body fat

Women with > 30-35% body fat

Men with > 25% body fat

Increased risk for health problems

Are usually overweight

Measurements using calipers

Estimation of Body Fat

Underwater weighing

Most accurate

Fat is less dense than lean tissue

Fat floats

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Estimation of Body Fat

Bioelectrical impedanceLow-energy current to the body that measures the

resistance of electrical flowFat is resistant to electrical flow; the more the resistance,

the more body fat you haveX-ray photon absorptiometry

An X-ray body scan that allows for the determination of body fat

Infrared lightAssess the interaction of fat and protein in the arm muscle

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Body Fat Distribution

Upper-body (android) obesity--”Apple shape”

Associated with more heart disease, HTN, Type II Diabetes

Abdominal fat is released right into the liver

Fat affects liver’s ability to clear insulin and lipoprotein

Encouraged by testosterone and excessive alcohol intake

Defined as waist to hip ratio of >1.0 in men and >0.8 in women

Body Fat Distribution

Body Fat Distribution

Lower-body (gynecoid) obesity--”Pear shape”

Encouraged by estrogen and progesterone

Less health risk than upper-body obesity

After menopause

upper-body obesity appears

Overweight and Obesity

Underweight = BMI < 18.5

Healthy weight = BMI 18.5-24.9

Overweight = BMI 25-29.9

Obese = BMI 30-39.9

Severely obese = BMI >40

An Epidemic of Obesity

OBESITY

• 61% of adults in the United States were overweight or obese (BMI > 25) in 1999.

• 13% of children aged 6 to 11 years and 14% of adolescents aged 12 to 19 years were overweight in 1999. This prevalence has nearly tripled for adolescents in the past 2 decades.

• The increases in overweight and obesity cut across all ages, racial and ethnic groups, and both genders.

• 300,000 deaths each year in the United States are associated with obesity.

• Overweight and obesity are associated with heart disease, certain types of cancer, type 2 diabetes, stroke, arthritis, breathing problems, and psychological disorders, such as depression.

• The economic cost of obesity in the United States was about $117 billion in 2000.

Juvenile-Onset Obesity

Develops in infancy or childhood

Increase in the number of adipose cells

Adipose cells have long life span and need to store fat

Makes it difficult to loose the fat (weight loss)

Causes

poor dietary patterns

lack of physical activity

43% of adolescents watch 2 hours or more of TV/day

Adult-Onset Obesity

Develops in adulthood

Fewer (number of) adipose cells

These adipose cells are larger (stores excess amount of fat)

If weight gain continues, the number of adipose cells can increase

Causes of Obesity

Nature debate

Identical twins raised apart have similar weights

Genetics account for ~40% of weight differences

Genes affect metabolic rate, fuel use, brain chemistry

Thrifty metabolism gene allows for more fat storage to protect against famine

Causes of Obesity

Nurture debate

Environmental factors influence weight

Learned eating habits

Activity factor (or lack of)

Poverty and obesity

Female obesity is rooted in childhood obesity

Male obesity appears after age 30

Nature and Nurture

Obesity is nurture allowing nature to express itself

Location of fat is influenced by genetics

A child with no obese parents has a 10% chance of becoming obese

A child with 1 obese parent has a 40% chance

A child with 2 obese parents has a 80% chance

Nature Vs. Nurture

Those at risk for obesity will face a lifelong struggle with weight

Gene does not control destiny

Increased physical activity, moderate intake can promote healthy weight

Why Diets Don’t Work

Obesity is a chronic disease

Treatment requires long-term lifestyle changes

Dieters are misdirected

More concerned about weight loss than healthy lifestyle

Unrealistic weight expectations

Why Diets Don’t Work

Body defends itself against weight loss

Thyroid hormone concentrations (BMR) drop during weight loss and make it more difficult to lose weight

Activity of lipoprotein lipase increases making it more efficient at taking up fat for storage

Why Diets Don’t Work

Weight cycling (yo-yo dieting)

Typically weight loss is not maintained

Weight lost consists of fat and lean tissue

Weight gained after weight loss is primarily adipose tissue

Weight gained is usually more than weight lost

Associated with upper body fat deposition

Why Diets Don’t Work

Weight gain in adulthood

Weight gain is common from ages 25-44

BMR decreases with age

Inactive lifestyle

Changes in body composition

Fluid is usually the first weight lost

Loss in lean body tissue means lowering the BMR

Very little fat is lost during weight loss

Lifestyle Vs. Weight Loss

Prevention of obesity is easier than curing

Balance energy in(take) with energy out(put)

Focus on improving food habits

Focus on increase physical activities

What It Takes To Lose a Pound

Body fat contains 3500 kcal per pound

Fat storage (body fat plus supporting lean tissues) contains 2700 kcal per pound

Must have an energy deficit of 2700-3500 kcal to lose a pound per week

Do the Math

To lose one pound, you must create a deficit of 2700-3500 kcal

So to lose a pound in 1 week (7 days), try cutting back on your kcal intake and increase physical activity so that you create a deficit of 400-500 kcal per day

- 500 kcal x 7 days = - 3500 kcal = 1 pound of weight loss

day week in 1 week

Sound Weight Loss Program

Meets nutritional needs, except for kcal

Slow & steady weight loss

Adapted to individuals’ habits and tastes

Contains enough kcal to minimize hunger and fatigue

Contains common foods

Fit into any social situation

Chang eating problems/habits

Improves overall health

See a physician before starting

Cutting Back

Control calorie intake by being aware of kcal and fat content of foods

“Fat Free” does not mean “Calories Free” (or “All You Can Eat”)

Read food labels

Estimate kcal using the exchange system

Keep a food diary

Regular Physical Activity

Fat use is enhanced with regular physical activity

Increases energy expenditure

Duration and regularity are important

Make it a part of a daily routine

Behavior Modification

Modify problem (eating) behaviors

Chain-breaking

Stimulus control

Cognitive restructuring

Contingency management

Self-monitoring

Cognitive Restructuring

Changing your frame of mind regarding eating

Replace eating due to stress with “walking”