If you have a choice between losing weight by doing more exercise and losing weight by eating less, then the first option is best, for a number of reasons. One reason is less well known and was described in 2006 by nutritionists at Washington University in Archives of Internal Medicine: weight loss by exercising more is better for your bones.
The researchers divided 48 somewhat podgy adults, average age 57, into three groups. One group ate as healthily as possible for one year [HL], the second group went on a calorie-reduced diet for a year [CR] and the third group exercised more for a year [EX]. The subjects in the diet group ate 16-20 percent less than they burned each day; the subjects in the exercise group burned 16-20 percent more than they ate each day.
The diet group lost 11 percent of their bodyweight; the exercise group 8 percent.
At the end of the year the researchers measured the subjects’ bone mass density using X-rays. In the figure immediately below you can see that the more weight the subjects lost, the more bone mass they also lost.
The figure above shows the bone mass of the subjects in the exercise group. There is no relationship between the number of kilograms lost and a decrease in bone mass.
“Exercise-induced weight loss is associated with preservation of BMD at important clinical sites of fracture”, the researchers write. “Therefore, exercise has the important advantage over CR by protecting against bone loss. However, because the amount of exercise required to achieve clinically meaningful weight loss is large, a more practical approach for weight reduction is a combination of caloric restriction and exercise. Our results suggest that regular exercise should be included as part of a comprehensive weight loss program to offset the adverse effects of caloric restriction on bone.”