Effect of Dietary Carbohydrate Source in Controlling Voluntary Physical Activity in Rats

Abstract

The effect of dietary carbohydrate on voluntary physical activity at two calorie intake levels was studied in 50 male Sprague-Dawley rats obtained at 100 days of age. Ten were randomly selected and killed to determine initial body composition and serum levels of cholesterol and insulin. Two groups of 20 rats each were fed diets which were nutritionally identical except for their carbohydrate component. In one diet, the sole carbohydrate source was cornstarch while the second diet contained a mixture of carbohydrates representative of the American “market basket” diet. Ten animals consuming each diet were fed ad libitum and 10 were fed 70% of ad libitum intake. All rats were housed in rotating treadmill activity cages during the 60 days of the study after which they were killed and changes in body and serum composition determined. The rats fed the diet containing the mixture of carbohydrates showed a greater amount of voluntary running when restricted to 70% of ad libitum intake than was found in any of the other three groups. This elevated voluntary activity was reflected in reduced serum insulin and cholesterol levels in this group. The fat/protein ratio of the weight gain was somewhat reduced in this group, but allowing all rats voluntary activity reduced the fat/protein ratio of the gain to < 1.0 in all groups. The results seem to indicate that increased spontaneous activity is triggered at two different levels of food deprivation when different dietary carbohydrate sources are fed.