This investigation quantified body composition and aerobic capacity and examined the interrelationships of these measures in 20 morbidly obese females (M age = 34.6 yrs) prior to gastric bypass surgery. Fifteen subjects were hydrostatically weighed at residual lung volume in order to determine body composition. Eighteen subjects performed a maximal modified progressive treadmill test to determine aerobic capacity. Results indicated that the 15 subjects who were weighed hydrostatically were heavier (M wt = 132.34 kg) and fatter (M % fat = 53.18) than any previously described individuals. Relative weight, which is used as a criterion to determine surgery eligibility, was not significantly (p > .05) correlated to percent body fat. Mean aerobic capacity (V̇O2 = 14.99 ml • kg-1 mir-1) was comparable to Class III cardiac patients and was limited by the individuals’ extreme body weight. Since relative weight was shown to be an insensitive measure of obesity, it is recommended that percent fat be measured and used as a means to determine eligibility for gastric bypass surgery. Further study of these individuals is warranted in order to determine what effects large weight loss following surgery will have on parameters of body composition and aerobic capacity. Understanding how large weight loss affects these parameters will aid in designing effective postsurgical exercise rehabilitative programs for future patients.
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