EFFECT OF EXERCISE AND DIETARY-PROTEIN LEVELS ON SOMATIC GROWTH, BODY-COMPOSITION, AND SERUM-LIPID LEVELS IN ADULT HAMSTERS

The role of increased protein intake in the acceleration of growth in adult female hamsters during, and immediately following, voluntary exercise, was examined in a 2 x 2 factorial experiment with the variables of physical activity (exercise or sedentary condition) and dietary protein levels (18 or 39%). Cornstarch and casein were added to a commercial powdered stock diet to produce 18 and 39%-protein diets, respectively. Two groups of seven hamsters (an 18 and 39%-protein group) were sedentary throughout 92 days, while the other two groups (n=7) had access to voluntary disc activity during the first 47 days and were retired from activity for the remaining 45 days. Protein intake of all hamsters was maintained at the same level. Increased intake of energy during the 47 days of exercise and first 29 days of retirement of the exercised group was supplied by cornstarch. On day 45 of retirement, prior exercise was associated with increased somatic growth, increase in serum concentrations of cholesterol, and no changes in the percentage of body fat and protein. On day 92, increase in the protein content of the diet was associated with increased percentage of body fat, decreased percentage of body protein, increased concentration of serum cholesterol, and no acceleration of somatic growth. Serum triglyceride levels were not changed. We conclude that the acceleration of growth associated with voluntary exercise in adult hamsters does not result from increased protein intake.