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 Needs
Direct 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 hypothalamus
When feeding cells are stimulated, they signal
you to eat
When satiety cells are stimulated, they signal you
to stop eating
Sympathetic 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 Y
Increases food intake
Reduces energy expenditure
Hormonal Influence
Endorphins
Natural body tranquilizer that can prompt you to eat
CCK
Along with gastrointestinal distention, decreases hunger
(and desire to eat)
Serotonin
Neurotransmitter 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)
[Ht (in m)]2
OR
Body wt (in lbs) x 703.1
[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
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
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 impedance
Low-energy current to the body that measures the
resistance of electrical flow
Fat is resistant to electrical flow; the more the resistance,
the more body fat you have
X-ray photon absorptiometry
An X-ray body scan that allows for the determination of
body fat
Infrared light
Assess the interaction of fat and protein in the arm muscle
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”