The effect of excessive weight loss on skeletal muscle in man. A study of obese patients following gastroplasty.

Lean body mass, muscle biochemistry, enzymehistochemistry and muscle strength were analyzed before and after 10% and 18% body weight loss following gastroplasty in 16 obese patients. Subjective fatigue was also determined, using an arbitrary scale, before and after the operation. Lean body mass and alkali-soluble proteins (non-collagenic proteins) per DNA decreased significantly in the postoperative period. The proportions of type I and type II muscle fibers remained normal postoperatively. The muscle fiber area decreased significantly at 10% body weight loss, with a tendency towards restoration at 18% weight loss, despite continuing loss of lean body mass. Preoperatively the muscle strength, determined as maximum voluntary concentric and eccentric action of the knee extensor and flexor muscles, was not significantly different from that in sedentary, age-matched subjects, but was less than expected from the lean body mass, content of alkali-soluble proteins and muscle fiber size. Muscle strength was not significantly changed postoperatively. According to the fatigue scale, the patients' wellbeing was improved at 18% body weight loss compared with the preoperative status.