Effects of weight changes produced by exercise, food restriction, or overeating on body composition.
The body weight of rats was reduced by exercise or by restriction of food intake over a period of 18 wk. Body composition was studied to determine if exercise protects against the loss of lean tissue that can occur as a result of a negative caloric balance. Rats weighing 706 +/-14 g were divided into four groups matched for weight. A baseline group was killed at the beginning of the study. An exercising group, fed ad lib., was subjected to a program of swimming. A sedentary, free-eating group was provided with food ad lib. Two sedentary, paired-weight subgroups were calorie restricted so that they lost weight at the same rate as the exercisers. The protein intake of one paired-weight subgroup was matched with that of the exercising group. The other sedentary, paired-weight animals ate the standard diet. There was no significant difference in body composition between the two sedentary, paired-weight subgroups which were, therefore, pooled for comparison with the other groups. The exercisers lost 182+/-19 g as a result of both an increase in caloric expenditure and a decrease in appetite. The sedentary, food-restricted animals lost an average of 182+/-18 g. The sedentary, free-eating animals gained 118+/-13 g. The carcasses of the exercised animals contained significantly less fat and more lean tissue than those of the sedentary, paired-weight animals, providing evidence for a fat mobilizing and protein conserving effect of exercise. The composition of the body substance lost by the exercising animals was 78% fat, 5% protein, 1% minerals, and 16% water, compared to 62% fat, 11% protein, 1% minerals, and 26% water for the sedentary, food-restricted rats. Fat accounted for 87% and water for 10% of the weight gained by the sedentary, free-eating animals.
D000818:Animals; D001823:Body Composition; D001835:Body Weight; D002241:Carbohydrates / Q000032:analysis; D004038:Diet, Reducing; D004044:Dietary Proteins; D004435:Eating; D005508:Food Deprivation; D008053:Lipid Mobilization; D008055:Lipids / Q000032:analysis; D008903:Minerals / Q000032:analysis; D009765:Obesity / Q000378:metabolism; D005082:Physical Exertion; D011506:Proteins / Q000032:analysis; D051381:Rats; D013550:Swimming; D014867:Water / Q000032:analysis
D002241:Carbohydrates; D004044:Dietary Proteins; D008055:Lipids; D008903:Minerals; D011506:Proteins; D014867:Water
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