ADA: Prevent Diabetes by Walking Just 30 Minutes a Day

Overweight, middle-aged people who don't exercise are at high risk of Type II diabetes, but modest exercise alone can improve their odds.

That's the word from Florida researchers who followed 18 previously sedentary, overweight subjects for six months. They presented their findings recently at the American Diabetes Association's Scientific Sessions in San Francisco.

Glen E. Duncan, a postdoctoral research fellow at the University of Florida who led the study, says risk factors declined just by adding the exercise and not improving the diet.

"Even though they did not lose weight, their insulin sensitivity improved nearly twofold from when they started," Duncan says.

The better a person's insulin sensitivity, the lower the risk of getting Type II diabetes, which now affects about 8 percent of U.S. adults. The more insulin-resistant a person is, the higher the risk.

The Florida research follows a much larger study released last year in the New England Journal of Medicine, in which more than 3,000 subjects in the Diabetes Prevention Program reduced their risk of Type 2 diabetes by 58 percent if they adopted intensive lifestyle changes, including a low-fat diet and daily exercise.

The more recent study suggests, however, that exercise alone may be a good start.

The subjects in the Florida study were, on average, 52 years old and had body mass indexes (BMIs) of nearly 29. A person who is 5-foot-10 and weighs 200 pounds has a BMI of 29, as does someone who is 5-foot-2 and weighs 160 pounds.

Duncan and his colleagues assigned the men and women to different exercise groups. Everyone walked for 30 minutes a session, but some walked at higher frequencies -- almost five to seven days a week compared to three to four -- and higher intensities -- 65 percent to 75 percent of their aerobic capacity versus 45 percent to 55 percent.

The researchers told the subjects not to try to lose weight, just to focus on the exercise. After six months, the researchers took tests such as glucose tolerance tests and noted BMIs. While the BMIs did not change, the subjects' insulin sensitivity improved greatly. Levels of an enzyme that helps in fat metabolism improved, too, Duncan says.

While those at risk for Type 2 diabetes should also eventually try to lose weight, Duncan says exercise may be the best and easiest place to start. "People have a hard time doing two things, diet and exercise. And even modest amounts of exercise in the absence of weight loss reduces the risk factors for Type 2 diabetes," he says.

The study makes sense to another expert who often cares for those with Type 2 diabetes and counsels others on how to avoid it.

"It's an important study because any time you can document something [of benefit] we can relay that into clinical practice," says Dr. Katja Van Herle, chief of endocrinology at Santa Monica-UCLA Medical Center.

"When you use skeletal muscle [during workouts] it allows insulin to be more effective at opening the cell door to get the sugar in [from the bloodstream]," she says. "As we gain more fat cells and don't exercise our skeletal muscles, the doors to the cells get 'stuck.' The pancreas makes more insulin. Sugar levels rise. This study underscores the importance of exercise at reversing this insulin resistance."

Another expert, Cathy Mullooly, a certified diabetes educator at the Joslin Clinic in Boston, praises the length of the study. "This study reinforces the preventive aspects of exercise," she says.

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