Exercise, Food Intake and Body Weight in Normal Rats and Genetically Obese Adult Mice

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Abstract
When mature rats accustomed to a sedentary existence were exercised in a treadmill for increasing daily periods, no increase in food intake was observed for low durations of exercise (20 minutes- 1 hour), but the food intake actually decreased slightly but significantly, as did body weight also. With longer durations of exercise (1-5 or 6 hours), food intake increased linearly and weight was maintained. For very long durations, the animals lost weight, their food intake decreased and their appearance, deteriorated. The 3 ranges of activity might be termed sedentary, normal, and exhaustive. Both the sedentary and the exhaustive can be considered "non-responsive ranges" with respect to food intake. When nonobese and genetically obese mice, all accustomed to a sedentary exercise were exercised on a treadmill for 1 hour a day, the exercise did not affect the weight of the normal mice but considerably decreased the weight gain of obese mice, even though the latter responded to exercise with increased food intake. Comparison of degrees of reactions to exercise of normal rats and mice show that there are some species differences; similarly, comparison of obese and goldthioglucose mice show that there are differences in degree of reaction to exercise in different types of obese animals. The importance of considering exercise, as well as food intake, in problems of obesity is again illustrated by these results.