A new study led by researchers at Fred Hutchinson Cancer Research Center has found that regular yoga practice may help prevent middle-age spread in normal-weight people and may promote weight loss in those who are overweight.
The study -- the first of its kind to measure the effects of yoga on weight -- appears in the July/August issue of Alternative Therapies in Health and Medicine.
Funded by the National Cancer Institute, the study involved 15,500 healthy, middle-aged men and women who were asked to complete a written survey recalling their physical activity (including yoga) and weight history between the ages 45 and 55. The study measured the impact of yoga with weight change, independent of other factors such as diet or other types of physical activity.
The researchers found that between the ages of 45 and 55, most people gained about a pound a year, which is a common pattern as people age and do not adjust their caloric intake to their declining energy needs. "However, men and women who were of normal weight at age 45 and regularly practiced yoga gained about 3 fewer pounds during that 10-year period than those who didn't practice yoga," said Alan R. Kristal, Dr.P.H., the study's lead author. For the study, regular yoga practice was defined as practicing at least 30 minutes once a week for four or more years.
But the researchers noted the greatest effect of regular yoga practice was among people who were overweight. "Men and women who were overweight and practiced yoga lost about 5 pounds, while those who did not practice yoga gained about 14 pounds in that 10-year period," said Kristal, a member of the Hutchinson Center's Public Health Sciences Division and a professor of epidemiology at the University of Washington School of Public Health and Community Medicine.
What accounts for yoga's apparent fat-fighting potential? Kristal, himself a longtime yoga student, 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 practice 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 practice yoga in a way that's not aerobic enough to burn a lot of calories, so it has to be some other reason."
One reason, she speculates, could be that yoga cultivates a form of gentle inner strength. "When we practice yoga, although it may look easy, there is some mild discomfort. You bring your body to a physical edge that's just a little bit challenging. And people who regularly practice yoga develop the inner resources to stay with a little bit of discomfort. They develop a softness inside and an ability to stay mindful. So that when you go home after yoga class and open up the fridge and see a chocolate cake, you have the resources to stay with the discomfort of not eating that chocolate cake."
Whatever the reason behind the apparent impact of yoga on weight maintenance and loss, Kristal stresses that these findings need to be replicated.
"I think it's time now to do a carefully controlled, randomized clinical trial to see if adding yoga to a standard weight-loss program can help people lose more weight or keep it off longer. The other message, particularly to people who might be overweight, is that yoga is a noncompetitive activity. It's something that everybody can do. It brings so many benefits, and if one of the clinical benefits is that it can help you control your weight, then that's a great thing."
The participants in the yoga study were part of a larger ongoing Hutchinson Center study involving more than 75,000 residents of western Washington called the Vitamins and Lifestyle, or VITAL, study. This $4.2 million project, which began in 2000, aims to determine whether vitamin, mineral or herbal supplements reduce the risk of cancer.