Energy balance of rats with lateral hypothalamic lesions.

Rats with lateral hypothalamic (LH) lesions maintain body weight at a chronically reduced percentage of nonlesioned controls. An assessment of how they achieve energy balance at subnormal weight levels entailed a determination of both their energy intake and their energy expended or lost in processing ingested food, on basal heat production, on activity, and in feces or urine. It was found that the caloric intake and expenditure of LH-lesioned animals, though significantly lower than those of controls, were appropriate to the reduced metabolic body size (BW0.75) that they maintained. Likewise, energy expenditure in the LH-lesioned animals was normal in that the proportion of their ingested energy relegated to 1) basal metabolism, 2) the processing food, and 3) activity was the same as that of nonlesioned controls. Thus, unlike nonlesioned rats, which at lowered body weights both decrease their energy needs and reorder the pattern of energy expenditure, LH-lesioned animals display a normal pattern of energy utilization at reduced weight levels. These findings provide further evidence that lateral hypothalamic mechanisms play an important role in setting the level at which body weight is regulated.