In a larger study, 383 men performed 25 minutes of strength exercise and 25 minutes of endurance exercise, two or three days a week, for eight weeks (Westcott and Guy, 1996). This combination exercise program produced a 6.4-pound fat loss and a 3.7-pound muscle gain, for a 10-pound change in body composition.

These are impressive improvements for two months of basic exercise, so these men must have been in pretty good shape to start with, right? Actually, only a small percentage of the participants began the program with a desirable body composition. The rest started at varying levels of over-fatness.

As presented in Table 1, the men were divided into five categories based on their initial body fat assessment: (1) less than 15% fat; (2) 15-19% fat; (3) 20-24% fat; (4) 25-29% fat; and (5) 30% plus fat. You will note that the men's entry bodyweights averaged about 20 pounds heavier in successive categories, ranging from 169.9 lbs. to 247.9 lbs. You will also notice that the body composition improvements were greater in successive categories, ranging from a 1.1 to a 6.3 decrease in percent fat. It should be noted that it was difficult to obtain accurate body fat measurements on the most obese participants, rendering their results less reliable.