Effect of Age and Dietary Carbohydrate Source on the Responses of Rats to Forced Exercise

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Abstract
Two experiments were conducted to study the effect of dietary carbohydrate source on the responses of rats of two different ages to forced exercise. The first experiment was begun with weanling rats and the second was begun with 150-day-old rats. Each experiment involved 80 male rats, 40 of which were fed a high fat diet supplying the carbohydrate as starch while the other 40 were fed an identical diet except that the carbohydrate was a mixture of starch and sugars commonly found in the human diet. Half of the animals receiving each diet were force-exercised by daily treadmill running for one-fourth of a mile while the other half remained sedentary. Each experiment was of 8 weeks' duration after which responses to the treatments were compared. In both studies exercise significantly reduced food intake, body weight gain, liver weight, the concentration of lipid and cholesterol in the liver, serum insulin level and the fat content of the carcass. In both studies, among the exercised animals, those fed the diet containing a mixture of starches and sugars tended to gain more or lose less body fat than those fed the cornstarch diet. Among the sedentary animals those consuming the cornstarch diet tended to gain more or lose less body fat than those fed the carbohydrate mixture. The influence of age on the diet-exercise interaction was minimal, as the responses of both young and mature rats to forced exercise were modified similarly by the source of dietary carbohydrate.