Diet and body weight loss in the rat during calorie restriction.

Abstract

With adult male rats, experiments were carried out to ascertain the different effects, if any, of isocaloric diets high in carbohydrate, fat, or protein fed in restricted amounts of 9 g per rat per day on body weight loss and composition. It was observed that the nature of the diet did not alter rate, amount, or composition of body weight loss when fed in restricted amount for a period of 12 days. Further, the nature of the diet did not alter significantly the following parameters during restriction: water intake, urine volume, resting metabolic rate, spontaneous activity, urine and feces calorie values. In an experiment with hypothalamic-obese rats, the body weight loss and composition were not significantly different among the dietary-restricted groups. An important observation in this experiment was that as body fat decreased markedly owing to restricted feeding, body water increased markedly and counterbalanced approximately 60% of the potential weight loss due to the decrease in body fat. Our reported observations do not support the hypothesis that the composition of the diet may determine the rate and amount of body weight loss as a consequence of restricted food intake. They do support the hypothesis that the calorie intake, not the nature of the source of calories, determines the rate and amount of weight loss, at least for relatively short periods of food restriction.