Reduced sexual dimorphism in upper arm muscle circumference associated with protein-deficient diet in a South American population.

Abstract

AbstractAnimal experiments have demonstrated that individuals exhibit differing tendencies to arrest growth and resorb muscle tissue under nutritional stress. Since placental and adrenocortical hormones are active in promoting muscle tissue resorption, sex differences may exist.In order to identify such sex differences, the upper arm circumferences of 362 individuals, aged one to 60 years, living in an area of chronic protein‐calorie malnutrition were compared by age and sex with published data collected from U.S. and highland Peruvian populations.Sexual dimorphism for arm muscle circumference in the malnourished population is less than in U.S. samples of comparable age‐categories. The highland population is closer to U.S. samples in the degree of dimorphism. The reduction in muscle circumference of males in the malnourished population appears to be the cause of the comparatively greater similarity of the sexes where protein‐calorie malnutrition is experienced from infancy through adolescence. High muscle relief and excellent tonus in these same males indicate that reduced muscle circumference is not the result of flaccidity or higher ratios of compressible fat to muscle tissue.Reduction of muscle tissue in undernourished males is a reduction in total metabolic demand. Such reductions are adaptive in areas of chronic nutritional stress.