Body Composition

Body composition refers to the make-up of your body. It's the relationship between A) your lean mass, which includes bones, organs, ligaments & muscles, and B) your fat mass. Body composition is a much better indicator of health than the scales. The scales only reflect how much you weigh, they don't take into account how much of your weight is composed of fat. Think of a 200 lb person who has 40% body fat vs a 200 lb person with only 12% body fat. The scale says each weighs 200 lbs, but one person has 80 lbs of fat, while the other has only 24 lbs of fat. That's quite a difference!

There are a variety of methods to assess health risks related to your body composition: BMI, Waist to Hip Ratio, and Body Fat Percentage. Of the three methods, Body Fat Percentage is the most accurate way to determine your lean to fat ratio. No matter which of the above methods you use, it's important to understand that either too much fat or too little fat is unhealthy. Obesity (too much fat) raises your risk of getting heart disease, diabetes, high blood pressure, sleep apnea and cancer. Too little fat can alter hormone levels, cause osteoporosis, digestive disorders, damage kidneys, create poor immune function, heart problems and in extreme cases cause organ failure and even death.

A healthy individual needs some essential fat. The National Institute for Health suggests that for men, 12-18% is considered a healthy amount of fat. For women the range is 16 - 25%. This essential fat is stored in order to allow for muscular activity. Remember, in order for a muscle to contract, it must have access to ATP, adenosine triphosphate. When ATP is broken down it creates energy so the muscles can contract. There is a small amount of ATP stored in each muscle, enough for a couple seconds of movement. After those few seconds are up, your muscle needs more ATP. Your body then breaks down glycogen, which is stored in your muscles and liver. After the glycogen stores are gone, fat is used to create ATP. If there is not enough fat to break down, the body will start to break down muscle to get enough energy. In the U.S. breaking down muscle in order to create ATP is not a health issue. Most people do not have the problem of too little fat. For most Americans, the problem is too much fat. Obesity has become a major health issue in the U.S. In 1980 40% of Americans were overweight or obese. In 2003 that number rose to an astonishing 66.9% of the U.S. population being overweight or obese.

When you eat more calories than you expend in a day, the excess calories are converted and stored as fat. This fat is not the good, essential fat. This unhealthy fat is stored either subcutaneously (under the skin - you can grab this fat with your hand) or viscerally (around the organs) Of these two types of undesirable fat, visceral fat is the worst, because it surrounds the organs and is harder to lose than subcutaneous fat and is tied to increased risks for cardiovascular diseases and Type 2 diabetes.

Remember, in order to be healthy, we don't want to be overweight or we don't want to be thin. We want to be lean. Let's look at three methods for assessing body composition: A) Body Mass Index, B) Weight to Height Ratio and C) Body Fat Percentage.

A) Body Mass Index (BMI)

Body Mass Index, BMI, is a relationship between your height and weight. It is an easy way to find out if you are at a healthy weight, but it doesn't take into account body composition, thus it may overestimate body fat in athletes and other people who have a very muscular build. It may also underestimate body fat in people who have lost muscle mass due to sarcopenia. When you have a high BMI, you have more weight per unit of height. A normal BMI is in the range of 18.5 - 24.9. You can calculate your BMI by using a hand-held device or at the NHLBI website at

Below 18.5
18.5 - 24.9
25.0 - 29.9
Obesity - Class 1
30.0 - 34.9
Obesity - Class 2
35.0 - 39.9
Obesity - Class 3
40.0 and above

B) Waist Measurement & Waist to Hip Ratio

Waist measurements are a good indicator of abdominal fat, which is a predictor of a person's risk for developing heart disease and other diseases associated with being overweight. To find your waist measurement, measure your waist above your hipbones, where it is the narrowest. A women with a waist measurement of greater than 35 inches or a man with a waist measurement of greater than 40 inches each run a greater risk for developing heart disease and other diseases.

Waist measurements are also used when calculating Waist to Hip Ratio. Waist to Hip Ratio is calculated by dividing the waist circumference by the hip circumference. Hip circumference is measured at the widest point of your hips. Waist to Hip Ratio, WHR, compares the proportion of body fat stored on your waist compared to body fat stored at your hips and buttocks. This is a simple measurement of fat distribution. Research has shown that individuals with extra weight located around the waist can be at higher risk for diseases such as heart disease and diabetes compared to those who carry more of their weight around their hips and thighs. For men, a ratio of .90 or less is considered safe. For women, a ratio of .80 or less is considered safe.

C) Body Fat Percentage

Finding out your body fat percentage can help you set realistic goals for a healthy weight. When you decide to lose weight, you do not want to lose lean body mass, you only want to lose some of the fat. Body fat percentage can be determined by handheld devices, underwater weighing, air displacement, X-ray, and skinfold calipers. The percentage of body fat that is considered healthy changes as you age. This chart is based on NIH/WHO guidelines for BMI and Gallagher et al. American Journal of Clinical Nutrition, Vol. 72, Sept. 2000.

Very High
< 21
21 - 32.9
33 - 38.9
>= 39
< 23
23 - 33.9
34 - 39.9
> = 40
< 24
24 - 35.9
36 - 41.9
> = 41
< 8
8 - 19.9
20 - 24.9
>= 25
< 11
11 - 21.9
22 - 27.9
>= 28
< 13
13 - 24.9
25 - 29.9
> = 30


Methods for Determining Body Fat Percentage

How to Improve Your Body Composition

After most people calculate their body fat, the first thing they want to do is improve their body composition. It's important to realize body composition is related to the calories consumed vs the calories expended in a day. In order to maintain your current weight, calories input must equal calories expended. To lose weight you must expend more calories than you consume. One pound of fat contains about 3500 calories of energy. If you reduce your food intake by about 500 calories a day, you will lose 1 pound of fat each week. Take the following points into consideration as you work to improve your body composition.

How Many Calories Do I Need A Day

As you attempt to determine how many calories you need to consume in a day, there are three acronyms you need to know: BMR, RMR and TEE. BMR assumes you are resting in bed. RMR assumes you are sitting around and eating. TEE assumes you are active. Let's take a closer look at each of these acronyms.

BMR - Basal Metabolic Rate is the minimum amount of energy a body needs to sustain life. BMR can be expressed in Watts or kilocalorie's. The more lean tissue you have, the higher your BMR. Actual BMR calculations are done in a laboratory setting after the person has slept for 8 hours and fasted for 12 hours. BMR assumes that you are not digesting food, you are not moving, you are just lying down in bed. If you are not very active, BMR will account for about 70-80% of your total energy expenditure. The larger the person, the higher the BMR. Younger people have a higher BMR than older people.

RMR - Resting Metabolic Rate is the minimum amount of energy your body needs to support the basic functions required to keep you alive. RMR assumes you are eating, digesting food, and moving around. This number is more representative of how many calories an inactive person needs to sustain life. In testing situations, the person usually has their RMR tested in the morning after having slept at home. RMR & BMR usually differ by about 10%. If you know your RMR, you will know how many calories you need to consume to maintain your current body weight. RMR is influenced by age, gender and body composition. Men generally have a higher RMR than women. As you age, your RMR goes down. People with more lean muscle mass have higher RMRs than people with more fat mass. This is because at rest, one pound of muscle can burn up to 70 times more calories a day than one pound of fat. Think about how many more calories a day 10 pounds of muscle would burn!

TEE - Total Energy Expenditure is higher than your Resting Metabolic Rate. TEE takes into account your physical activity during the day. Other factors such as temperature, stress, and medication can affect your TEE.

Estimating RMR & TEE

Since it takes tests to determine RMR and BMR, there are several equations which will give you an approximate value. There might be as much as a 10% error with these predictions. People who are under 18 years of age, pregnant or lactating women or individuals who's metabolism is affected by disease or medication should not follow RMR & TEE estimations. We'll look at two methods for estimating RMR and one for estimating TEE. Note: People who are under 18 years of age, pregnant or lactating women or individuals who's metabolism is affected by disease or medication should not follow these RMR & TEE estimations.

Harris Benedict Equations to estimate RMR - The Harris Benedict equations were created by two scientists and are commonly used for calculating RMR in healthy individuals. This equation was developed in 1919 and doesn't take into consideration muscle mass. One criticism of this estimation is that there weren't many obese people in the sample used to estimate RMR.

A)  Convert body weight to kilograms:
    _____ lb / 2.2 kg/lb = _____ kg

B)  Convert height to centimeters:
    _____ in x 2.54 cm/in = _____ cm

C)  Use appropriate equation to calculate BMR (Basal Metabolism Rate). 

RMR = 655 + (9.56 x ____ kg) + (1.85 x ____ cm) - (4.68 x ____ yr) = ______ cal/day

RMR = 66.5 + (13.8 x ___ kg) + (5 x ___cm) - (6.76 x ___yr) = ______ cal/day

(That's not a typo, the Men's formula is 66.5 and the Women's formula is 655)


World Health Organization Equation to estimate RMR - The World Health Organization, WHO, is part of the United Nations system. It is responsible for providing leadership on global health matters, shaping the health research agenda, setting norms and standards, articulating evidence-based policy options, providing technical support to countries and monitoring and assessing health trends. In 1985 Schofield researched and developed the following formula for estimating RMR.

A)  Convert body weight to kilograms:
    ______ lb / 2.2 kg/lb = ______ kg

B) Find the appropriate formula in the table below and calculate your RMR. 

 RMR = ( ______ x ______ kg) + ______ = _____ cal/day

Age Range (yrs) Equation to Derive
RMR in cal/day
Equation to Derive
RMR in cal/day
(17.5 x wt) + 651
(12.2 x wt) + 746
18-30 (15.3 x wt) + 679 (14.7 x wt) + 496
30-60 (11.6 x wt) + 879 (8.7 x wt) + 829
Over 60 (13.5 x wt) + 487 (10.5 x wt) + 596







Estimating TEE - Your total energy expenditure takes into account your resting metabolic rate and the amount of activity participated in each day. Remember that these equations can be off by as much as 10%. In order to maintain your current weight, the amount of calories you get from your food must equal the amount of calories you expend each day. One pound of fat contains about 3500 calories of energy. If you reduce your food intake by about 500 calories a day, you will lose 1 pound of fat each week.

To estimate your TEE multiply your estimated RMR times your Activity Factor (from the table below)
TEE = RMR x Activity Level

Activity Level Activity Factor for Men Activity Factor for Women
Sedentary - Sitting most of day, working on a computer, playing cards, watching TV, reading
Lightly Active - 3 hours of light activity a day (walking, golf, laundry) and 1 hour of moderate activity (tennis, walking briskly, aerobics)
Moderately Active - 2 hours of moderate activity per day (jogging 5 - 6 miles)
Very Active - Moderate intensity activity for most of the work day or running 9 - 13 miles per day
Extremely Active - High level of physical activity for most of the work day or running 14 - 17 miles a day



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"Those who think they have not time for bodily exercise
will sooner or later have to find time for illness. "
Edward Stanley