Factors in the reduced food intake of rats fed a low-protein diet

Abstract
Male rats of the Wistar strain were fed either a control (20% casein) or a low-protein (5% casein) diet. Following the intraperitoneal injection of glucose solution it was observed from the blood glucose curve that low-protein fed rats had a delayed or impaired utilization of this carbohydrate. Resting oxygen consumption was not significantly different, and after glucose injection the slight increase in both groups was not significant. On refeeding after fasting, the colonic temperature of low-protein fed rats rose to a greater extent than did that of controls. Administration of protamine zinc insulin (PZI) decreased colonic temperature during fasting particularly in low-protein fed animals, and also during refeeding following a brief fasting period. From the results of these several experiments, it would appear that low-protein fed rats may have (a) an impairment in utilization of carbohydrate, and (b) a defect in immediate energy dissipation or an increased rate of energy production from ingested food. These two abnormalities may contribute to the reduced food intake of such animals. The association of a greater increase in colonic temperature on feeding and the hypophagia of rats fed a low-protein diet, as well as the hypothermic effect of PZI associated with an increase in food intake are suggestive of a thermostatic control of food intake in addition to a glucostatic control.

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