Lecture  |  Study Guide | 

Major Assignment 

Lecture  

Energy Balance and Body Composition (pp. 312 - 335)
(On the syllabus this is our week 4)

Energy balance looks like this:

                          Energy in = Energy out

Theoretically, if a person ate 3000 kcal/day and was active to the tune of 3000 kcals/day, over time the person would have no change in body weight.

Theoretically, if a person ate 4000 kcal/day and was active to the tune of 2000 kcal/day, over time the person would gain weight.

Theoretically, if a person ate 2000 kcal/day and was active to the tune of 3000 kcal/day, over time the person would lose weight.
However, nothing is this simple . . .

If we look at energy expenditure (how we use energy/kcals), 
~ 65% of our kcals go for basal metabolism,
~ 25% go for physical activity, and 
~ 10% for the thermic effect of food.

The energy expended/used by the body is the sum of all the energy needed for body functions. The energy used can be categorized based on whether it is needed to maintain basic body functions, to fuel physical activity, or to process the nutrients consumed in food.  

Basal Metabolic Rate (BMR)
The energy needed for maintenance of basic body functions such as breathing, circulating blood, and maintaining a constant body temperature makes up 60-75% of the body's total energy requirement. This portion of the energy requirement is called the basal metabolic rate (BMR), which is the minimum amount of energy needed to keep an awake, resting body alive.  BMR includes the energy necessary for all essential metabolic reactions and life-sustaining functions, but it does not include the energy needed for physical activity or for the digestion and absorption of food. BMR measurements must be performed in the morning in a warm room before the person rises, and at least 12 hours after food intake or activity.  Because of the difficulty of achieving these conditions, measures of basal needs are usually made after only 5 or 6 hours without food or exercise.  These measures yield values referred to as resting energy expenditure (REE) or resting metabolic rate (RMR). The difference between BMR and RMR values is less than 10% in most cases.
RMR is affected by factors such as body weight, lean body mass, gender, growth rate, and age.  BMR may also be affected by low-energy diets. Energy intakes below needs may depress BMR by 10-20%, or the equivalent of 100-400 kcals per day.  This drop in BMR decreases the amount of energy needed to maintain weight. So it makes intentional weight loss more difficult.

You might ask, "How can I raise my BMR?" so that I expend more energy/kcal. The answer: engage in endurance events and in strength building activities regularly to maximize lean body tissue. Lean tissue/muscle uses/expends kcals, fat tissue does not. 

When kcal intake is too low or too few CHOs or Protein is consumed, the body will degrade lean tissue (muscle) to meet glucose and protein needs.

The body stores body fat if the kcal intake is too high or if the fat intake is too high.

1 lb. body fat = 3500 kcals

People seem to gain more body fat when they eat extra fat kcals than when they eat extra CHO kcals.

People seem to lose body fat when they limit fat kcals.

Physical Activity
Physical activity is the second major component of energy expenditure. It represents the metabolic cost of external work, which includes the energy needed for exercise as well as for the functions of daily life, such as sitting, standing, and walking. For most people, physical activity accounts for 15-30% of energy requirements, but this varies greatly.
The energy required to perform an activity, such as walking, increases with increasing body weight because it takes more energy to move a heavier body. Energy requirements also depend on how strenuous the activity is and the length of time it is performed. A professional athlete who spends many hours a day training at a strenuous activity level uses a great deal more energy in daily activities than does an office worker who spends most of his day sitting at a desk. 

For information about the energy requirements of various activities, go to:
www.primusweb.com/fitnesspartner/   (click OK and then CANCEL if asked for personal information; you'll be granted access)

Thermic Effect of Food (TEF)
The thermic effect of food is the increase in energy expenditure above BMR that occurs during the several hours after the ingestion of food. This effect is due to the metabolic cost of digesting food and absorbing, metabolizing, and storing nutrients form the meal. These processes cause body temperature to rise slightly for several hours after eating. The energy required for TEF is estimated to be about 5-10% of energy intake but can vary depending on the amounts and types of nutrients consumed. 
Because it takes energy to store nutrients, TEF increases with the size of the meal.  A meal that is high in fat has a lower TEF than a meal high in CHO or protein, because oxidizing and/or storing dietary fat is only 2-3% of the energy consumed, whereas the cost of using amino acids by either oxidizing them or incorporating them into proteins is 15-30% of the energy consumed, and the cost of oxidizing CHO or storing it as glycogen is 6-8%.  The difference in the cost of storing energy means that a diet high in fat may produce more body fat than a diet high in CHO.  In other words, you body is very efficient at handling fat-it uses fewer kcals to process fat than protein or CHO, leaving more fat kcals for fat storage.

Estimating Energy Requirements
Energy needs can be estimated by totaling the approximate amount of kcals used for 
BM + physical activity + TEF.

The following activities are for practice only. You will not submit the results to me.

Activity 
A.  Estimate your energy requirements (EERs) using the formulas on pg. 319.

Change your weight in lbs. to kilograms. 
To do this divide your weight in pounds by 2.2. For example: 150 lbs /2.2 = 68 kg.

Change your height from inches to meters.
To do this divide inches by 39.37. For example: 71 in. / 39.37 = 1.8 m.

Find your Physical Activity (PA) Factor from the Physical Activity (PA) Estimates chart on pg. 320.

Plug all this information into the equation to determine an estimate of your energy requirements.

B.  Compare your EERs from above with "Pounds per Inch Shortcut for Estimating Healthy Body Weight" on pg. 324. How do both numbers compare?

Body Composition
The body is composed of lean body mass and body fat. Lean body mass or fat-free mass includes bone, muscles, and all tissue except fat tissue. Body fat, or adipose tissue, lies under the skin and around internal organs.  The amount of fat an individual carries and where that fat is deposited are affected by age and genetics as well as by energy balance.  
At birth, body fat is about 12% of body weight and increases in the first year of life. During childhood, as muscle mass increases, body fat decreases. During adolescence, females gain proportionately more fat and males gain more muscle mass. As adults, women have more stored body fat than men. A healthy level of body fat for a young adult female is between 20-30% of total weight; for young adult males, it is between 12-20%. There is an increase in body fat during pregnancy to provide energy stores for the mother and fetus.  With aging, lean body mass decreases; between the ages of 20 and 60, body fat typically doubles even if body weight remains the same.  This occurs regardless of energy intake.  Some of this loss of lean body mass can be prevented by increasing physical activity.

Fat located under the skin is called subcutaneous fat, and that deposited around the organs is called visceral fat. Generally, fat in the hips and lower body is subcutaneous (this is referred to as lower body fat/pear shape), whereas fat deposited around the waist in the abdominal region is primarily visceral fat (this is referred to as upper body fat/apple shape). Where an individual deposits body fat is determined primarily by their genes.  Gender, age, and environment also influence where fat is stored.  Visceral fat storage is more prevalent in men than in women. But after menopause, visceral fat increases in women. Stress, tobacco use, and alcohol consumption predispose people to visceral fat deposition, whereas physical activity reduces it. The distribution of body fat affects the risks associated with carrying excess body fat.  Excess visceral fat is associated with a higher incidence of heart disease, high blood pressure, stroke, diabetes, and breast cancer.

A person's waist circumference is an indicator of fat distribution and abdominal fat.
Generally, a women with a waist circumference of greater than 35 inches and men with a waist circumference of greater than 40 inches have a high risk of central obesity-related health problems. See Figure 10-14 on pg. 326.

Activity:
Calculate your waist-to-hip ratio. Divide the waistline measurement by the hip measurement. In general, women with a waist-to-hip ratio of 0.80 or greater and men with a waist-to-hip ratio of 0.90 or greater have a high risk of health problems.
What is your ratio?

A healthy body weight is defined by 3 criteria:
* A weight within the suggested range for height.
* A fat distribution pattern that's associated with a low risk of illness and premature
   death.
*A medical history that reflects an absence of risk factors associated with obesity, such
  as elevated blood cholesterol, blood glucose, or blood pressure.

  Activity:
     Body mass index (BMI):  an index of weight in relation to height.
     Look at the BMI Chart (Table 10-1) on page 323.
     Find your height on the left; look for your weight in pounds to the right.
     Look at the top of the chart to determine if you're
     a healthy weight, overweight, or obese. At the top of the chart are
     numbers from 19-40; this is the BMI number.

     Above Table 10-1, find a BMI number and silhouettes (body shapes.
     What are the limitations of using the BMI?

Calculate your BMI at Shape Up America: if asked for personal information, click OK and then CANCEL; you'll be granted access.
http://www.shapeup.org 

Other measures of body composition include: fat fold measures, hydrodensitometry, bioelectrical impedance, etc.

Learn about the 10,000 Steps Program at Shape Up America: if asked for personal information, click OK and then CANCEL; you'll be granted access.
www.shapeup.org

Calculating your body mass index (BMI) and waist-hip ratio (WHR) gives you valuable personal information about how the issues of body weight and body composition relate to you.

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Study Guide -
This is a tool for your use. You will not submit your responses to the instructor.

1. How many kcal are in one pound of body fat? How many kcal per day must a person
   expend (or take in) to lose (gain) one pound of weight in a month?

2. What information does a bomb calorimeter provide? What do direct and indirect
   calorimetry measure?

3. How much energy spent in a day comes from basic metabolic functions? What factors
   raise basic metabolic rate (BMR)? What factors lower BMR? What three factors affect
   energy needs during physical activity? How does body weight affect energy
   expenditure? How does the activity's duration, frequency, and intensity affect energy
   expenditure? Define the thermic effect of food. How much energy per day comes from
   the thermic effect of food? Define adaptive thermogenesis.

4. What components of energy expenditure are considered when calculating estimated
    energy requirement? To estimate energy spent on BMR, what factors are used? What
    steps are taken to estimate energy output for an individual?

5. What criteria are used to define "healthy" body weight?

7. Define body mass index (BMI). What BMI is associated with overweight and obesity?
    What BMI is associated with the lowest risk to health for younger and older adults?
    What two pieces of information does BMI fail to measure? Based on BMI, how is ideal
    body weight determined? What is a reasonable target for most overweight individuals?

8. What is the percent body fat range for a normal-weight man and for a normal-weight
    woman? What is one important criterion for determining how much a person should
    weigh or how much body fat a person needs? At what percent body fat do health
    problems generally develop in men and women whose ages are below and above forty
    years? How does fat distribution relate to increased risk for disease? What is "central"
    obesity? What is meant by "apples" and "pears" relative to fat distribution? What is the
    most valuable and practical indicator of fat distribution and abdominal fat? How many
    inches around the waist indicates higher risk for obesity-related problems? What is a
    desirable value for women based on waist-to-hip ratio? For men?

9. Briefly describe 3 methods used to assess body composition, in addition to waist
     circumference and waist-to-hip ratio.

10. What health risks are associated with being underweight? How many people die
     annually from obesity-related diseases? Explain the relationship between overweight
     and the following: cardiovascular disease, type 2 diabetes, and cancer.

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