Food restriction postpones, not prevents, exercise-induced growth in hamsters

Voluntary exercise during ad libitum feeding accelerates growth in mature female hamsters. If food is restricted during the exercise period, growth is suppressed, but ad libitum access to food at the cessation of exercise permits rapid catch-up growth in length and weight during retirement. To see whether the exercise-induced stimulus to grow persists when food-restriction is continued during retirement, female golden hamsters were matched by weight and assigned to exercise (EX) and sedentary (SED) groups fed ad libitum and to corresponding activity groups (REST-EX, REST-SED) food-restricted to 80% of starting weight. At the end of each week for 3 weeks following retirement, one REST-EX and one REST-SED group were fed ad libitum. At 21-35 days post-refeeding, mean gains in length and weight of each exercise group were greater (p < 0.05) than the gains of the corresponding sedentary group. Thus, exercise under food restriction remained an effective stimulus for acceleration of growth throughout three weeks of continued food restriction beyond termination of exercise, and ad libitum feeding permitted the delayed expression of exercise-induced catch-up growth in hamsters.