| Calorie restriction, without malnutrition, is known to be the most effective intervention for increasing maximal lifespan in a variety of animal species. To better understand the long-term effects of calorie restriction on aging nonhuman primates, the Wisconsin National Primate Research Center (WNPRC) had begun a study in 1989 with 30 male rhesus monkeys and later added 16 male and 30 female rhesus monkeys in 1994. Monkeys were randomly selected and subjected to a restriction of 30% from their individual baseline caloric intakes or allowed to feed ad libitum diets. Data were systematically collected on these animals and this database formed the basis of three studies.; To determine if the animals altered the absorption efficiency of food under calorie restriction, we measured the metabolizable energy intake (MEI) in calorie restricted (CR) rhesus monkeys provided 30% less calories than control (C) monkeys of comparable age. Food intake was measured to obtain accurate measures by accounting for food waste in the pans beneath cages. Since moisture content could be a variable factor depending on the hygroscopic nature of the feed, we measured the moisture to be a two-fold greater than the factory defined values accounting for some error in actual food eaten by these monkeys. Two 24-hr fecal and urinary energy losses were assessed using bomb calorimetry along with the gross energy of feed. The amount of excretory (urine + feces) energy lost was not significantly different in the CR compared to C monkeys but the coefficients of digestion and metabolizable energy were significantly lower by 4% (p<0.001) in the CR monkeys. The measured MEI calculated after accounting for food intake measurements, urinary and fecal losses differed by 16% (p<0.001 between CR and C monkeys) as against the desired 30% restriction. The total energy expenditure (TEE) in these animals differed by 8% with changes in body composition accounting for less than 1.5% of MEI. Nonetheless, all the animals were in energy balance.; Because rhesus monkeys can develop obesity and diabetes, they have been studied as a useful model for discovering anti-obesity and anti-diabetic treatments. To aid our comparison with human data, longitudinal data collected over 8-14y from 40 male and 26 female rhesus monkeys were analyzed to define body mass indexcrown-rump-length (BMICRL) for underweight and obesity in rhesus monkeys. We determined the %body fat ranges to be 9-23% in male and 8-18% in female monkeys corresponding to BMICRL of 32-44kg/m2 for male and 27-35kg/m2 for female monkeys. (Abstract shortened by UMI.)... |
