Influence of reversible obesity on eating behavior, blood glucose, and insulin in the rat

Excessive food intake, resulting in extreme obesity, was induced in rats by electrical stimulation (three 30-min sessions per day for 3 wk) of the lateral hypothalamus (LH). Outside the stimulation sessions no voluntary food intake occurred duringthese weeks. In the subsequent recovery period, accurate records of spontaneous feeding were made. Blood levels of glucose, insulin, and free fatty acids (FFA)were determined during the stimulation period as well as the recovery period. Duringfeeding elicited by electrical stimulation of the LH in the obese phase, there was alarge increase in the glucose level. The insulin level, very high in the intervals between the stimulation sessions, showed no change, a small decline, or a large decrease,respectively, during stimulation in the morning, the afternoon, or the night. If food was withheld during stimulation, there was a large increase in the glucose level and alarge decrease in the insulin level. The first spontaneous meal after the termination of stimulation was extremely postponed, viz, until the glucose and insulin levels returned to normal for the first time. The insulin response to the first spontaneous mealwas exaggerated. Although in the following period (about 10 days) a rapid decrease inbody weight occurred, food intake was only minimal. The insulin level was high and the glucose levelsubnormal during that period. The insulin and glucose levels were normal again only after recovery of normal body weight and food intake. It is tentatively concluded that the regulation of body energy stores (body weight) is achieved through the control of food intake by circulating insulin and glucose levels.