The slow stretches and meditations of yoga don't burn calories like a run on the treadmill. But a new study suggests it might help people keep weight off in middle age. Researchers found that overweight people in their 50s who regularly practiced yoga lost about five pounds over 10 years, while a group in the same age range gained about 13 1/2 pounds over the same period. Middle-aged people of normal weight generally put on pounds over 10 years, but those who did yoga gained less weight than those who didn't practice yoga.