Anthropometric (height, weight, and skinfolds), biochemical (serum proteins, albumin, and cholesterol), metabolic (nitrogen balance and creatinine excretion), hematological (plasma volume, hemoglobin, hematocrit, bone marrow hemosiderin, percent transferrin saturation, vitamin B12, and folic acid) variables and body water compartments (total and extracellular) have been measured in 49 adult male subjects who exhibited a wide range of nutritional states from normal to severely undernourished. Changes in body composition associated with moderate degrees of nutritional compromise were related principally to decreases in body cell mass (-15%). Body fat was normal. With severe nutritional involvement, both fat depots (-29%) and body cell mass (-29%) were significantly diminished. Muscle cell mass was more affected than other cells in the body (-41%). These data could indicate that in the group with moderate compromise, energy reserves (and hence energy balance) were maintained but dietary protein deficiencies were not compensated for. Both calorie and protein deficiencies were evident in the subjects with severe undernutrition. Multiple regression equations (r greater than 0.8) were developed that allow prediction of muscle cell mass, fat-free weight, and body cell mass from simple anthropometry and serum albumin levels. Decreases in serum albumin concentration were best related to deficits in muscle mass (r = 0.77).

Six well-trained endurance athletes were studied to determine if submaximal treadmill exercise results in increased plasma levels of beta-endorphin/beta-lipotropin (Bh-Ep/Bh-LPH) immunoreactivity. Bh-Ep/Bh-LPH immunoreactivity was measured by radio immunoassay in plasma from six experienced runners before and after 30-min treadmill runs at a self-selected pace, 60 and 80% VO2 max, and a control experiment of 30 min rest. All tests were randomized and occurred during the same time of day for a given subject (0600--1500 h). Preexercise Bh-Ep/Bh-LPH values averaged between 10 and 20 pg/ml and increased two- to fivefold after each run. The increase was statistically significant (P less than 0.05) only after the 60% run when Bh-Ep/Bh-LPH increased to a mean of 58.3 pg/ml. A large individual variation in the Bh-Ep/Bh-LPH response to running was noted. Mood state and perceptual data were also collected, and no significant relationship with Bh-Ep/Bh-LPH was evident. These data suggest that the stress of treadmill running acts as a stimulus to greater Bh-Ep/Bh-LPH secretion, a reduction in its degradation, or a combination of these, which leads to increased levels of these ligands in venous blood. The physiological significance of these increased plasma levels is not clear.

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