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Just a Half-Hour Walk Keeps Pounds Off

Study finds benefits of modest daily exercise without diet change

MONDAY, Jan. 12, 2004 (HealthDayNews) -- Want to foil that one- or two-pound yearly weight gain that eventually turns many of us into overweight or obese Americans?

Commit to a half-hour walk or other moderate exercise every day, and that will prevent the gain -- and perhaps lead to a modest loss, according to the results of a new study published in the Jan. 12 issue of the Archives of Internal Medicine.

"Thirty minutes is enough," says Cris Slentz, an exercise physiologist and senior research scientist at Duke University Medical Center in Durham, N.C., and the lead author of the study.

This modest amount of exercise can prevent weight gain and sometimes lead to minor weight loss without changes in diet, he says, adding more exercise can result in weight loss in overweight exercisers, he says.

Slentz says his study findings suggest that the 60 minutes of daily exercise suggested in 2002 by the Institute of Medicine may not be needed to prevent weight gain.

For the study, Slentz and his team assigned 120 subjects, ages 40 to 65, who exercised less than once a week and were overweight or obese, to one of four groups for eight months. Some did no exercise, some did low-dose moderate activity such as walking 12 miles a week, some did low-dose vigorous activity such as jogging 12 miles a week, and some did high-dose vigorous activity such as jogging 20 miles a week. Subjects could choose to exercise on treadmills, elliptical trainers, or stationary bikes.

They didn't change their diets and they were asked to maintain their starting body weight. If they dropped 2.5 percent or more of their body weight, a nutrition counselor advised them on how to increase it back to starting levels.

The high-dose, vigorous exercise group lost 3.5 percent of their weight, while the two low-dose groups had a 1 percent loss. The no-exercise group had a 1.1 percent weight gain.

"Thirty minutes daily is enough to prevent weight gain and lead to modest weight loss," says Sletz. By modest, he means about two pounds over six months.

The half hour a day is not going to make an overweight person look sculpted, he cautions. And the 30 minutes should be devoted to aerobic exercise that elevates the heart rate for the duration of the workout (such as walking or jogging), not strength training (such as lifting weights). "Weight training burns about half as many calories as does aerobic training," he says.

Probably the easiest exercise for sedentary people is walking, Slentz says. He suggests walking at a moderate to brisk pace, covering about 2 miles in a half hour.

Another expert calls the new research "an important study." But John Jakicic, an exercise research expert at the University of Pittsburgh and director of the university's Physical Activity and Weight Management Research Center, has a concern about the research.

When body weight fell by 2.5 percent, the diet was altered to bring the subject back to starting weight. "Thus it is unclear if this is the real effects of exercise on weight," he says.

But Slentz counters that the body weight only fell that much in the high-vigorous group, not in the less active groups.

Jakicic, who has studied the topic extensively, says, "I think that the message should be that to prevent weight gain an individual should start with at least 30 minutes of at least moderate intensity exercise per day." If that doesn't prevent gain, it may be necessary to increase to as much as 60 minutes or more per day, he says.

And if that still does not prevent gain, diet changes should be started, he adds.

More information

For information on how to make time for exercise, try the American Council on Exercise or the President's Council on Physical Fitness and Sports.

SOURCES: Cris Slentz, Ph.D., exercise physiologist, senior research scientist, Duke University Medical Center, Durham, N.C.; John M. Jakicic, Ph.D., associate professor and director of the Physical Activity and Weight Management Research Center, University of Pittsburgh; Jan. 12, 2004, Archives of Internal Medicine
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