Traditional yoga isn't a primary weight-loss exercise, although some Internet sites have touted it as such. Yoga involves performing postures during which you pay special attention to your breathing — exhaling during certain movements and inhaling with others. It can help improve flexibility and endurance and reduce stress.

Unlike aerobic activity, yoga doesn't increase calorie burning very much — although some may advocate a modified version, called power yoga, that is aerobic. One hour of traditional yoga usually burns less than 200 calories. Also, yoga doesn't significantly increase lean muscle mass, such as strength training does, which can also help you burn more calories.

Some yoga positions can actually be harmful. They can put excessive stress on the lumbar spine. This is a concern especially if you have a condition such as osteoporosis. These positions may increase the risk of vertebral compression fractures and lower back injuries.

The most effective way to lose weight is with a combination of a sensible diet, aerobic exercise and strength training.