For athletes, reducing percent body fat should be the focus of weight-loss efforts rather than reducing total body weight, otherwise optimum performance will be compromised. In some cases, total weight may not even change, when percent body fat goes down and muscle goes up. (Muscle weighs more than fat.) Therefore, assessing body composition is crucial as you determine your weight-loss goals.

This example uses Emily to illustrate. Emily is a 24-year old runner who’s training for a marathon. She feels she could improve her performance if she lost some weight. Until a few years ago, she weighed about 120. Emily is 5 feet and 4 inches tall and now weighs 135 pounds. Her present estimated body fat is 23 percent. Her body fat goal is 15 percent.

Here’s how she would calculate her optimal weight:

  1. 135 (current weight) x 23 percent (current % body fat) = 31 pounds of fat

  2. 135 (current weight) - 31 (weight that’s fat) = 104 pounds of lean

  3. FFM (fat-free mass) goal = 85 percent (difference between body fat goal and total body)

  4. 104 (current pounds of FFM) ÷ 85 percent = 122 (Emily’s goal weight)

Emily’s weight-loss goal is to reach 122 pounds and reduce her percent body fat from 23 percent to 15 percent.

Now plug in your own numbers:

  1. ________ (current weight) x ___% (current % body fat) = ____ pounds of fat

  2. ____ (current weight) - ____ (weight that is fat) = ____ pounds of lean

  3. FFM goal =___% (difference between body fat goal and total body)

  4. ____ (current pounds of FFM) ÷ ____% = _____ (Your goal weight)