What accounts for yoga's apparent fat-fighting potential? Kristal, himself a long time yoga practitioner, suspects it has more to do with increased body awareness than the physical activity itself.

'During a very vigorous yoga practice you can burn enough calories to lose weight, but most people don't practise that kind of yoga,' he said.

'From my experience, I think it has to do with the way that yoga makes you more aware of your body. So when you've eaten enough food, you're sensitive to the feeling of being full, and this makes it much easier to stop eating before you've eaten too much.'

Study co-author Denise Benitez, owner of Seattle Yoga Arts, agrees. 'Most people practise yoga in a way that's not aerobic enough to burn a lot of calories, so it has to be some other reason.'

These findings appeared in the August issue of Alternative Therapies in Health and Medicine.