Understanding Nutrition

							     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

•   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 low-
intensity electrical current.
Because electrolyte-
containing 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.