ENERGY-BALANCE IN RHESUS-MONKEYS (MACACA-MULATTA) SUBJECTED TO LONG-TERM DIETARY RESTRICTION

Male rhesus monkeys of various age groups representative of the specie s life span were fed ad libitum amounts (controls) or 30% less food th an control monkeys of comparable age and body weight. Despite signific antly lowered energy intake and body weight, the amount of energy lost in the feces, and fecal energy density (concentration) were trot alte red in diet-restricted (DR) monkeys, compared to age- and weight-match ed controls. Absolute energy expenditure (EE; 24-hr) was consistently lower in DR monkeys, but this trend was not statistically significant. Expressed as a function of metabolic mass (body weight, metabolic bod y size, lean mass), 24-hr EE was not different in monkeys subjected to long-term DR, compared to controls. Calculations of net energy (intak e - loss), as an index of energy balance, revealed that Energy expendi ture generally exceeded energy intake ill all juvenile and adult group monkeys. However, this discrepancy was not statistically different fr om zero, suggesting that most animals were in energy balance. Also, th ere was no difference between control and DR animals with respect to e nergy balance. Diet restriction induced significant reductions in the absolute amount of lean body mass; however, percent (of total weight) lean and fat mass did not differ from controls.