Energy Balance
Body Composition
Gaining & Losing weight
• Whether a person gains or loses
weight depends on:
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Energy intake vs. energy expenditure
Genetic factors
Childhood weight
Behavioral factors
Social factors
Energy Balance
• Energy balance
– Occurs when energy intake = energy
expenditure
– Energy intake = kcal from food
– Energy expenditure = energy expended
at rest + during physical activity
Energy Expenditure
• BMR
• Physical activity
• Thermic Effects
– Cost of food
processing
Energy Balance
• Basal Metabolic Rate (BMR)
– Energy expended to maintain basal, or
resting, functions of the body
• highest proportion of total energy expenditure
– More lean tissue increases your BMR
– BMR decreases with age
• ~3-5% per decade after 30
– Estimating BMR
• body weight (kg) * 1.0 kcal/kg/hour
So, obese people have lower
BMR, right?
Factors affecting BMR
Energy Balance
• Thermic Effect of Food (TEF)
– Energy expended to process food
– ~5-10% of total kcal of the meal
• 500 kcal meal costs 25 - 50 kcal to process
– Fats require little energy to digest,
transport & absorb
– Proteins & Carbs require more
Physical Activity
• 20-35% of total energy output
• Includes everything above basal level
– Sitting, standing, walking
• Moving large muscles requires more
Energy
• Calculating Energy expenditure:
– Energy Cost (kcal/kg/min) * Time (min)
• Do a couple
Genetic factors
• Different hypotheses explain the impact of
genetics on body fat
– Thrifty Gene Theory
– Set-point Theory
– Leptin Theory
Thrifty Gene Theory
• H1: individuals with the gene use less
energy (at all times) than people who do
not possess the gene
– More efficient fat storage
– Lower metabolic rates
• Evolutionary story: Protection against starvation
during lean times
• Applied to American Indian populations with high
rates of obesity & diabetes
– Evidence: No direct; little indirect
Set-Point Theory
• H1: Body is tuned to maintain weight
within a narrow range, or “set-point”
• Evidence:
– Body appears to maintain weight @ present
level
– Rebound weight gain among dieters
– Occasional over-eating often does not result
in weight gain
– Can change set point through consistent,
long term changes in diet & exercise
Leptin Theory
• Leptin: hormone produced by adipose
cells; goes systemic
– Binds to neurons in “satiety center” in brain;
inhibits neurons that stimulate feelings of
hunger
– Increased production reduces food intake,
body weight and body fat
Childhood weight
• Environmental factors in childhood
influence
– Food choices
– Activity levels
– Later adult behaviors
• Childhood overweight increases the risk
of heart disease and premature death as
an adult
Behavioral Choices
• Food Choices
– Composition of diet should remain balanced
– Overeating dietary fat increases obesity
faster than overeating carbs or proteins
– Why?
• Less energy required to digest fats than other
two
• More easily stored as adipose tissue…no
conversion necessary
Behavioral Choices
• Hunger vs. Appetite
– Appetite = psychological desire to eat;
cause overeating
– “Satiety mechanism” malfunction
• Hormone or sensory receptor malfunction
• Increase or decrease satiety
Social Factors
• Social factors influence our diet:
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Family or cultural traditions
Holidays and celebrations
Easy access to high-fat foods
Less physically active lifestyles
Societal expectations of the “perfect”
body
How many kcals do we need?
• Manual calculation:
– BMR (women) = body weight (kg) * 0.9 kcal/ kg/hour
– BMR (men) = body weight (kg) * 1.0 kcal/ kg/hour
• 77.3 kg * 1 * 24 = 1855 kcal
– Activity = some percentage of BMR; Ex: 70%
• 1855 kcal * 0.70 = 1299 kcal
• 1855 + 1299 = 3154 kcal
• How many are you eating? Recall:
– Fats:
– Carbs:
– Proteins:
9 kcal/gram
4 kcal /gram
4 kcal/gram
What is a healthful body
weight?
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Appropriate for your age
Maintained without constant dieting
Is acceptable to you
Based on family history of body shape
and weight
• Promotes healthful eating habits and
allows for regular physical activity
Evaluating body weight
•
Actual weight is not the only factor to
consider
•
Determining if a person’s body weight is
healthful should include:
1. Determining the Body Mass Index (BMI)
2. Measuring body composition
3. Assessing the pattern of fat distribution
Evaluating body weight
• Body Mass Index = BMI
– BMI = weight (kg) / height (m)2
– BMI values below 18.5 or above 30 have
increased risks of health problems
Excess Death among overweight people
Declining weight of Miss America
Distribution of Body Weights
in U.S. Adults
Healthy weight
(BMI 18.5–24.9)
Underweight
(BMI <18.5)
Overweight
(BMI 25–29.9)
Obesity
(BMI 30–39.9)
Extreme obesity
(BMI _>40)
Achieving & maintaining
healthy weight
• Healthful weight change requires
– Gradual change in energy intake
– Regular and appropriate physical
exercise
– Application of behavior modification
techniques
Losing weight
– Follow recommended serving sizes
– Reduce intake of high-fat and high-energy
foods (~20%)
– Regular physical exercise (of ANY kind will do, but
which kinds preferentially burn fat?)
• Increase energy expenditure
• Increase BMR
Gaining weight
– Eat 500 to 1,000 extra kcal/day
– Eat frequently throughout the day
– Maintain a balanced diet; keep fat intake to
25-30% of total energy intake
– Avoid tobacco products
• depresses appetite; increase BMR
– Regular exercise with resistance training
• Promotes conversion of calories to lean muscle
rather that fat
Gaining weight
• Supplements?
• Studies continue to show no effect of
AA and protein supplements:
– No gains in muscle mass and strength, nor in
performance
– Including androstenedione (Mark McGuire)
• Some effects of this supplement are increased
LDL:HDL levels (why bad?) & mood disturbances
• Also, those unfortunate (if you’re a male)
feminizing characteristics
Disorders & Energy intake
• Underweight: having too little body fat to
maintain health
– BMI less than 18.5 kg/m2
– Increases risk of infection and illness
• Overweight:
– BMI of 25 - 29.5 kg/m2
– Some health risks; most importantly, adopt
healthier lifestyle to avoid becoming obese
Obesity & Morbid obesity
• Obesity: Having excess body fat that
adversely effects health
• BMI 30 - 39.9 kg/m2
• BMI > 40 kg/m2 = morbidly obese
– Body weight exceeds 100% of normal
• Morbid obesity: body weight exceeding
100% of normal, creating a very high risk
for serious health complications
Increase in childhood obesity
Critical periods
• Weight gain in specific life stages have
strong effects on weight later in life.
• Weight gain in these periods increase
risk of adult obesity & related diseases
– Gestation & early infancy
– Ages 5-7
– Adolescence