Synergistic stimulation of food intake by simultaneous insulin and cold

Insulin administered to rats during simultaneous exposure to cold increases food intake by more than the sum of the separate feeding responses and prevents the normal cold-induced loss of body weight. On withdrawal of insulin with cold maintained, all the body weight maintained by insulin is immediately lost and body weight thereafter is identical to that of rats exposed to cold only. Accumulated food intake for the joint treatment and after withdrawal of insulin with cold maintained is greater than for cold exposure only. There is no increase in metabolic cost due to insulin. Energy density of weight gain during insulin treatment is high and of weight loss on withdrawal of insulin with cold maintained is very low. These responses do not conform with commonly proposed models of feeding control.