Metabolic rate and lipogenesis in weanling rats fed high carbohydrate diets

¹ Department of Physiology, University of Rochester School of Medicine and Dentistry, Rochester, New York

Weanling rats fed a 60% carbohydrate diet were observed to have a self-limiting elevation in oxygen consumption persisting for 6–9 days. This phenomenon was associated with a diminished food utilization during this interval. The calorigenic response was abolished by feeding the 60% carbohydrate diet in amounts just sufficient to maintain body weight for several days before ad libitum ingestion was permitted. Animals so treated develop some type of adaptation and are referred to as adapted animals. Further studies of this metabolic response were carried out on rats fed the high carbohydrate diet ad libitum at weaning and in other animals after such a period of adaptation. Unadapted weanling rats fed 60% carbohydrate diets ingest calories in excess of their capacity for efficient utilization. During ad libitum feeding, adapted animals were found to accumulate fat at a faster rate than unadapted animals. The evidence obtained is consistent with the conclusion that in the weanling rat lipogenesis is below achievable limits and becomes limiting with regard to food utilization when a high carbohydrate diet is fed. The calorigenic response appears to dissipate ingested calories above those utilizable for energy, including weight gain, and thus maintain a balance between caloric intake and expenditure.