Effects of Caloric Intake and Feeding Frequency on Carbohydrate Metabolism of the Rat

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Abstract
The relationship between quantitative nutrient intake and periodicity of food ingestion on the adaptations of carbohydrate metabolism was studied. Glucose and insulin tolerance tests were conducted on animals that had eaten ad libitum (controls), were pair-force-fed or force-fed 80% of the nutrient intake of the others. It was found that, compared with the controls, a) the underfed rat was more reactive, the fully-force-fed animal less responsive, to the hypoglycemic effects of insulin and b) the undernourished rat disposed of a glucose load at a faster rate, the pair-forcefed rat at a slower or equal rate. The results of glucose tolerance tests performed on relatively undernourished rats “trained” to eat for 2 hours/day or pair-fed animals eating aliquots of their ration hourly were similar. In vitro studies with diaphragms and epididymal fat pads (glucose uptakes and insulin sensitivities) of animals that had eaten ad libitum or were force-fed either 100% or 80% of the nutrient intake of the controls yielded data that do not appear to account fully for the in vivo findings. It is concluded that in studies of metabolic adaptations to altered feeding frequency, one should use pair-fed animals given “optimal” amounts of nutrients, which in this case required force-feeding to equalize intake at the ad libitum level.