a variety of mechanisms (that are discussed in later chapters), more so if exercise is not included.
In fact, if a person loses weight without exercising, over half of the total weight loss is muscle and
water, not fat.
Body Composition
More than changes in scale weight, we need to focus on overall change in body composition.
Body composition (or bodyfat percentage) represents the ratio of bodyfat to total body weight.
The body is generally divided into two components (1):
- Fat mass (FM): the sum of the body’s fat stores
- Lean body mass (LBM): everything else including bone, muscle, body water, minerals, the
brain, internal organs, muscle glycogen, etc.
Total bodyweight (TB) = FM + LBM
Therefore,
Bodyfat percentage = FM/TB
The ultimate goal in dieting is to see a drop in bodyfat percentage primarily through a
decrease in fat mass. Increases in lean body mass will also cause bodyfat percentage to
decrease.
A sample body composition estimation
An individual is measured and found to have 15% bodyfat at a bodyweight of 180 lbs. He
has:
180 lbs * 0.15 = 27 lbs of fat
180 lbs - 27 lbs = 153 lbs of lean body mass.
For an individual desiring a specific bodyfat percentage, there is an equation that will
determine how much fat must be lost assuming 100% of the weight lost is fat and there is no
change in lean body mass (2).
Desired bodyweight = lean body mass / (1-desired bodyfat).
Fat loss needed = current body weight - desired body weight.
So if our 180 lb., 15% bodyfat individual (with 153 lbs of lean body mass) wished to reach 10%
bodyfat, he would have to lose the following:
Body weight needed = 153 / (1 - .10) = 153 / 0.90 = 170 lbs
Fat loss needed = 180 lbs -170 lbs = 10 lbs fat loss.
Problems with the scale
The primary problem with the scale is that it does not differentiate between what is being
lost (or gained) on a diet. With regular exercise, especially weight training, there may be an