Walk a day helps keep flab at bay

Sorry, no shortcuts. You probably need at least a 30-minute walk every day if you hope to maintain weight without dieting, a new study finds.

Smaller increases in daily exercise, like a 15-minute walk, simply won't burn up enough calories to compensate for yearly weight gains seen among increasingly overweight populations, Swiss researchers reported Wednesday in the American Journal of Public Health.

Other research has suggested that if overweight people can increase daily exercise sufficiently to burn about 100 calories a day, or cut food intake by that much, they can fend off further weight increase.

For instance, Duke University researchers reported in January that the equivalent of 30 minutes of walking daily was sufficient to prevent weight gain in a group of otherwise inactive people in late middle age. However, the participants' caloric intake remained the same.

A pound of fat is equivalent to 3,500 calories.

How many calories are actually burned during a walk depends on how heavy the walker is, how far he or she walks and, to a lesser extent, how fast. Typically, a 150-pound person needs to walk a mile in 30 minutes or less to burn 100 calories.

Dr. Alfredo Morabia of Geneva University Hospitals, lead author of the new report, said: "If the specific goal is to approach expending 100 calories a day through walking, the duration should be closer to 60 minutes for slow walking and 30 minutes for moderate or brisk walking."

Morabia and colleague Michael Costanza took government data on the normal physical activity of adults between the ages of 35 and 74 in Geneva and calculated how many additional calories the city's population as a whole might burn if citizens added 15- or 30-minute walks to their daily lives.

The researchers found that adding just a slow 15-minute stroll would burn an average of nine calories a day, while a 30-minute stroll would increase the burn rate to 25 calories. But only with everyone taking a brisk 30-minute walk would the population's average calorie expenditure rise to 100 a day, the researchers said.

Even so, Morabia said daily walks of any duration would probably change the population's health for the better. "The walking habit may grow more rapidly once it has been adopted by a minority -- a snowball effect -- and may stimulate weight-reducing dietary changes as well."

Obesity has become a worldwide concern. The World Health Organization estimates that more than 300 million adults around the globe are obese, including some 115 million in developing nations. More than 25 percent of American adults are considered obese, according to U.S. health officials.

On the Net: www.ajph.org; www.who.int/nut/obs.htm

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