The study, published in the Journal of Applied Physiology and conducted by the University of Pittsburgh, examined 64 subjects between the ages of 60 and 75 years of age who were either overweight or obese and led a sedentary lifestyle prior to the start of the study. The subjects were assigned to three separate groups where the first group was required to exercise only, the second group to diet only, and the third to exercise and diet.
Exercise consisted of either walking on a treadmill or riding a stationary bicycle. The diet involved lowering caloric intake sufficiently to achieve a 10% loss in weight by the end of four months.
The study's findings were:
- By the end of the study, the exercise group spent fewer calories (i.e. became more efficient) on the exercise task than at the start of the study.
- The exercise and the exercise plus diet groups used more fat as the source of fuel for their body.
- Although the diet-only group weighed less by the end of the study, they did not gain any efficiency in performing the exercise task.
- The diet-only group lost both muscle and fat.
- The exercise plus diet group ended up being the most efficient at performing the exercise task by the end of the study, thus demonstrating an additive effect from dieting combined with exercise.
The important message here is that exercise allows the body to preferentially burn fat rather than muscle even when the body is reducing its caloric intake. By dieting alone, the body turns to burning both fat and muscle. This can be especially risky for seniors since they naturally lose muscle mass as they grow old and the loss of too much muscle loss can prevent them from carrying out their daily activities.