Skeletal muscle function during hypocaloric diets and fasting: a comparison with standard nutritional assessment parameters

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Abstract
Skeletal muscle function and standard nutritional assessment parameters were measured in six obese patients. Base-line measurements were made on a weight-maintaining diet, and further measurements after 2 wk of a 400-cal diet, followed by 2 wk of fasting and then after 2 wk of refeeding. The function of the adductor pollicis muscle was assessed by electrical stimulation of the ulnar nerve. The objective parameters of muscle function measured were: 1) force of contraction expressed as a percentage of the maximal force obtained with electrical stimulation at 10, 20, 30, 50, and 100 Hz. 2) Maximal relaxation rate expressed as percentage force loss/10 ms. 3) Endurance expressed as percentage force loss/30 s. Standard nutritional assessment parameters (serum albumin and transferrin, creatinine height index, anthropometry and total body nitrogen and potassium) were also measured. There was a significant increase in the force of contraction at 10 Hz from a base-line of 29.6 ± 1.0% to 49.0 ± 2.8% (mean ± SEM) after 2 wk of a 400-cal diet (p > 0.01). There was a significant slowing of the maximal relaxation rate from a base-line of 9.8 ± 0.3% force loss/10 ms to 8.2 ± 0.3% force loss/10 ms (mean ± SEM)(p > 0.01) after 2 wk of a 400-cal diet. After a further 2 wk of fasting these abnormalities in muscle function persisted. There was a significant increase in muscle force loss from a base-line of 3.9 ± 0.8% force loss/30 s to 13.7 ± 3.4% force loss/30 s (mean ± SEM) after fasting (p > 0.01). After 2 wk of refeeding all aspects of muscle function measured were normal. During the study the standard nutritional assessment parameters did not change significantly.