Food intake and body weight in rats with daily food-availability restrictions

Male Wistar rats were offered food for either 24, 6, or 1 h a day at two different ambient temperatures -21 or 6 degrees C. At room temperature, rats offered food for 6 h a day matched their food intake to that of rats with 24 h of food-availability in 2-3 days, so that no main changes in total food intake, gross food efficiency, and body weight were recorded. No impairment of thermoregulatory capacity was recorded as judged by the unaltered oxidative capacity of brown adipose tissue and skeletal muscle. Nonetheless, a transient hypothermia was recorded at the beginning of the experiment in the food-restricted group. Rats that were only offered food 1 h a day were unable to sustain the food intake of the control animals, so that a continuous decline in body weight and a negative gross food efficiency ensured. In the cold, the food intake of rats offered food for only 6 or 1 h a day was similar to that showed by the corresponding groups at 21 degrees C. These results suggest a maximum rate for digestive processes, irrespective of ambient temperature. However, such levels of food intake were clearly insufficient to cope with the thermoregulatory enhanced energy demand at 6 degrees C, ad judged by the decrease in body weight.