Body composition was studied in severely undernourished adult male inhabitants of a rural area of Colombia to evaluate the extent and the time course of the changes occurring upon nutritional repletion. During a 45-day basal period on a low (26g/day) protein diet containing adequate calories, body fat depots increased significantly (mean +/- SD = +3.02 +/- 2.9 kg), and there was a significant decrease in cell hydration from 81.8 to 76.4% (-5.4 +/- 9.1%). Upon protein repletion (100 g/day), cell hydration decreased significantly to 71.4%, while body cell mass increased markedly (9.0 +/- 1.1 kg). During protein repletion, muscle cell mass increased significantly (+5.5 +/- 0.6 kg) and rapidly, while the increase in nonmuscle cells (+3.5 +/- 3.8 kg) and specifically in red cell mass lagged behind. With repletion, the changes in the absolute values for plasma volume (+0.4 +/- 0.13 liters) were significant, but those in extracellular fluid volume (-0.7 +/- 1.9 liters) were not. Thus, the major compositional changes observed occurred in the body fat and the body cell mass components; these occurred independently of each other.
