Transcript No Slide Title

Understanding Nutrition
Chapter 8 - Energy Balance and
Body Composition
By
A. Fellah, Ph.D.
Energy Balance
When energy in balances with energy out, a person’s body
weight is stable.
For each 3500 kcal eaten in excess, a lb of body fat is stored.
The rate of wt. loss for overweight people is 0.5-2 lbs a week or
10% of body weight over 6 months.
Energy in: the kcalories Foods Provide
• Food Composition:
– Bomb calorimeter: an instrument that measures the
heat energy released when foods are burned, thus
providing an estimate of the potential energy of
foods.
– A food containing 12g CHO, 5g fat, and 8g protein
would provide 48 CHO kcalories, 45 fat kcalories,
and 32 protein kcalories, a total of 125 kcalories.
Bomb Calorimeter
• When food is burned, the chemical bonds between the carbons and
hydrogens are broken, and energy is released in the form of heat.
• The amount of heat generated provides a direct measure of the amount
of energy stored in the food’s chemical bonds.
• Food Intake:
– Hunger: the physiological drive for food that initiates
food-seeking behavior.
– Appetite: the integrated response to the sight, smell,
thought, or taste of food that initiate or delaying
eating.
– Satiation: the feeling of satisfaction and fullness that
occurs during a meal and halts eating. Determines
how much food is consumed during a meal.
– Satiety: the feeling of satisfaction that occurs after a
meal and inhibits eating until the next meal.
Determines how much time passes between meals.
• Overriding Hunger and Satiety Signals:
– Eating in response to arousals is called stress eating.
– Either negative or positive stress.
– Some people cannot eat during times of stress.
• Nutrients, Satiation, and Satiety:
– Satiating: having the power to suppress hunger and inhibit
eating.
– Protein is the most satiating.
• Message Central- The Hypothalamus:
– Hypothalamus: a brain center that controls activities such as
maintenance of water balance, regulation of body
temperature, and control of appetite.
Hunger
A cascade of regulation: hunger, appetite, satiation, and satiety
Hunger, Satiation, and Satiety: 1 of 2
Physiological influences, sensory influences, and cognitive influences.
Hunger, Satiation, and Satiety: 2 of 2
Postingestive influences and postabsorptive influences.
Satiety Scores
of Foods
How Fat Influences Serving Size: 1 of 2
Peanuts
Popcorn
For the same size serving, peanuts deliver more than 15
times the kcalories and 20 times the fat of popcorn.
How Fat Influences Serving Size: 2 of 2
Popcorn offers twice the satiety of peanuts. For the same number
of kcalories, a person can have a few high-fat peanuts or almost 2
cups of high-fiber popcorn. (This comparison used oil-based
popcorn; using air-popped popcorn would double the amount of
popcorn in this example.)
Energy Out:
the kCalories the Body Spend
Components of Energy Expenditure:
1. Basal Metabolism:
The energy needed to maintain life when a body is at complete
digestive, physical, and emotional rest.
• Basal Metabolic Rate (BMR): the rate of energy used for
metabolism under specified condition: after a 12 hr fast
and restful sleep. (kcalories/kg body weight/hr).
• Resting Metabolic Rate (RMR): a measure of a person at
rest in a comfortable setting, but with less stringent criteria
for the number of hrs fasting. RMR>BMR
• Lean Body Mass: the weight of the body minus the fat
content.
• Voluntary activities: conscious and deliberate muscular
work-lifting, walking, climbing,…….
2. Physical Activity:
• Voluntary movement of the skeletal muscles and support
systems.
• Most variable and most changeable components.
• Its influence on both weight gain and weight loss can be
significant.
3. Thermic Effect of Food: (TEF)
• An estimation of the energy required to process food
(digest, absorb, transport, metabolize, and store ingested
nutrients).
• The sum of the TEF and any increase in the metabolic rate
due to overeating is known as diet-induced thermo-genesis
(DIT).
4. Adaptive Thermogenesis:
• Adjustments in energy expenditure related
to changes in environment such as extreme
cold and to physiological events such as
overheating, trauma and changes in
hormone status.
Components of
Energy
Expenditure
Energy Process in the Body
Components of Energy Expenditure
• The amount of energy spent in a day differs for each individual, but in general,
basal metabolism is the largest component of energy expenditure (60 to 65%),
and the thermic effect of food is the smallest (only 10 %).
• The amount spent in voluntary physical activities has the greatest variability,
depending on a person’s activity patterns.
Components of Energy Expenditures
Each of these structures is made of 8
blocks. They weigh the same, but they
are arranged differently. If you were to
count the sides of these structures, you
would find that the short, wide one has
24 sides and the tall, thin one has 34.
Because the tall, thin structure has a
greater surface area, it will lose more
heat (expend more energy) than the
short, wide one.
Similarly, two people of different heights
might weigh the same, but the taller,
thin one will have a higher BMR
(expending more energy) because of
the greater skin surface.
Factors that Affect BMR
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Age: slowing the BMR
Height: Tall, thin -----Higher BMR
Growth: Children and pregnant women ---Higher BMR
Body composition: The more lean tissue –Higher BMR.
Fever: raises the BMR.
Stresses: raises the BMR.
Environmental temp.: Both heat and cold---raise BMR.
Fasting/starvation: lowers the BMR.
Malnutrition: lower the BMR.
Hormones: thyroxin speed up or slow down BMR.
Smoking: nicotine increases energy expenditure.
Caffeine: increases energy expenditure.
Sleeping: BMR is lowest when sleeping.
Body weight, Body Composition, and Health
• Body Composition: the proportions of muscles, bone, fat, and
other tissue that make up a persons total body weight.
Body weight = fat + lean tissue (including water).
• Body Mass Index (BMI): an index of a person’s weight in
relation to height, determined by dividing the weight (kg) by the
square of the height (m).
BMI = weight (kg)
height (m)2
• Overweight: body weight above some standard of acceptable
weight that is usually defined in relation to height.
Body Mass Index
BMI values and health risks
Mortality Data
The Effects of Body Weight and Smoking
Body Mass Index and Mortality
Both underweight
and overweight
present risks of a
premature death.
This J-shaped
curve describes the
relationship
between body
mass index (BMI)
and mortality and
shows that optimal
BMI is between 21
and 25 (some
researchers extend
this range from 19
to 27).
Body Fat and Weight
00
10 0
5
0
9
Fatfold Measures
The assessor measures
body fat by using a
caliper to gauge the
thickness of a fold of
skin on the back of the
arm (over the triceps),
below the shoulder
blade, and in other
places (including lower
body sites) and then
compares with
standards.
Hydrodensitometry
The assessor measures body
density by weighing the
person first on land and then
again while submerged in
water.
The difference between
provides a measure of the
body’s volume.
A mathematical equation
using the two measurements
allows to calculate body
density’ from which the
percentage of body fat can
be estimated
Bioelectrical Impedance
The assessor measures
body fat by using a lowintensity electrical current.
Because electrolytecontaining fluids, which
readily conduct an electrical
current, are found primarily
in lean body tissue, the
leaner the person , the less
resistance to the current.
The measurement to
electrical resistance is then
used in a mathematical
equation to estimate the
percentage of body fat.
Summary
• Energy balance is a simple yet complex formula.
• Energy from food and beverages is measured by the
use of the bomb calorimeter.
• Hunger, appetite and satiety resulting from stimuli from
nutrients and hormones play a role. Energy
expenditure includes basal metabolism, physical
activity, thermic effect of food and adaptive
thermogenesis.
• An individual can estimate energy requirements.
• If the energy consumed equals the energy expended,
the individual is in energy balance.
Summary
• If energy consumed is more than energy expended,
weight increases.
• If energy consumed is less that energy expended,
weight decreases.
• A variety of techniques are used to measure body weight and
body composition.
•
Height/weight charts and body mass indexes are used as
Guidelines for weight.
•
Waist circumference and waist-to-hip measure body fat
distribution.
Summary
• Fatfold measures, hydrodensitometry and
bioelectrical impedance measure body
composition.
• Body fat distribution and composition may be
critical in determining risks to health,
• Both overweight and underweight are conditions
associated with health risk.
• There is a strong relationship between obesity
and cardiovascular disease, diabetes cancer.