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increase in lean body mass as fat is being lost. Although body weight may not change, body
composition is changing.

Let’s say our 180 lb individual at 15% bodyfat begins a basic exercise program of weight
training and aerobic exercise. Over the first eight weeks, he gains 4 lbs of lean body mass and
loses 4 lbs of fat at the same time. Looking only at weight, nothing appears to have happened.
But looking at changes in body composition (in table 1), it is obvious that the program is working.

Table 1: Changes in body composition

Before After Change

Total weight (lbs) 180 180 No change

LBM (lbs) 153 157 +4

Fat (lbs) 27 23 -4

% bodyfat 15% 12.7% -2.3%

Individuals beginning a weight training program often gain one or two pounds by the scale
from increased water storage in the muscles. This weight gain is temporary and should not be
confused with true fat gain. Similarly, consuming carbohydrates after a period of low
carbohydrate dieting will cause a large, but transient, increase in bodyweight from increased body
water. This weight gain also should not be confused with true fat gain.

Although the measurement of body composition may not be convenient for many
individuals, as it requires special equipment, a similarly objective method exists: how clothes are
fitting. Many individuals beginning an exercise program, especially if it includes weight training,
will lose inches with no change on the scale. Since one pound of muscle takes up less space than
one pound of fat, this reflects a gain in muscle that equals or exceeds the loss of fat. Keep in mind
that a large gain in muscle may cause clothes to fit tighter and should not be misinterpreted as
fat gain.

Subcutaneous vs. Essential fat

Before discussing how body composition is measured, it is necessary to know where the
bodyfat is located. Total bodyfat is typically divided into subcutaneous fat (under the skin) and
essential fat (in the spine, brain and around the internal organs). Average levels for these two
types of fat appear in table 2 below along with the bodyfat levels recommended by health
organizations (1). Bodybuilders are included as a reference point only for those individuals
seeking extreme levels of leanness. In all likelihood, maintaining this level of leanness is
unhealthy, especially for women.