You've Got to Step Up Your Exercise Intensity and Time
to Stay Slim and Healthy

Americans need to get real when it comes to controlling their weight - some people may need to do an hour or more of physical activity a day, and intensity matters, obesity experts say.

The bar for exercise in the United States was once high, but almost a decade ago a moderate-activity alternative was offered that encouraged people to walk briskly or move more for a minimum of a half-hour a day.

The goal was to get sedentary Americans to do something, anything. But many people didn't realize that 30 minutes of activity might not keep their waistlines under control. Now the pendulum is swinging back.

A report last fall from the National Academy of Sciences' Institute of Medicine called for 60 minutes or more a day of activity to prevent weight gain and get additional health benefits. This advice comes as more than 120 million people in the United States are overweight or obese.

"People have got to stop kidding themselves about what it takes to control weight," says George Blackburn, associate director of the division of nutrition at Harvard Medical School. "They can't take a little stroll and think they are doing themselves any good. You need the intensity and you need the time, at least 60 minutes."

For about half of the time, you need to be doing something that makes you break a sweat and breathe heavily, he says. The rest can be 10-minute periods of more moderate activity.

James Hill, an obesity expert at the University of Colorado Health Sciences Center in Denver, says: "If everybody did 30 minutes of activity a day, it would be huge for public health. Would it make everybody lean? I don't think so."

Exactly how much exercise you need depends on genetics, muscle mass, your diet, how much you weigh, whether you've lost a lot of weight and other factors, Hill says. Most people will have to figure out for themselves exactly what it takes.

Still, only about a third of adults in the United States do enough to meet the moderate-activity guideline.

Experts have long debated the best exercise prescription. For years people were urged to get 20 to 60 minutes of continuous moderate- to high-intensity aerobic activity three or more times a week and to do weight training at least twice a week.

Then, in 1995, scientists said the research showed that adults would get health benefits from accumulating 30 minutes or more of moderate-intensity activity on most, preferably all, days of the week. People could walk briskly, swim, golf, rake leaves, dance, vacuum. The activity could be done in 10- and 15-minute segments, as long as it added up to 30 minutes or more. The bottom-line message: It's no sweat if you don't sweat.

Experts hoped this flexibility would appeal to sedentary Americans who had been left in the dust by the fitness craze. It was meant only to complement the earlier guidelines. People who wanted to work out longer were encouraged to do so.

But somewhere along the way the moderate-activity message got diluted.

"Some people have interpreted the guideline as 'anything counts,' " says Russ Pate, a professor of exercise science at the University of South Carolina. "That was not the intention and never was the intention."

For instance, dusting the house or strolling through the mall doesn't meet the standard. Intensity matters. The pace has to be challenging enough that you can feel your heart beat more rapidly and your breathing increase.

If you are meeting the 30-minute guideline and your weight is inching up, then you probably need to do more, Pate says.

Some people may have more success at weight loss and avoid putting the pounds back on if they do 45 to 60 minutes a day of moderate-intensity exercise, says JoAnn Manson, chief of preventive medicine at Harvard's Brigham and Women's Hospital in Boston.

They can lose weight by doing 30 minutes a day, but they may need to cut more calories, she says. Another option is to work out harder. Manson also recommends strength training at least 20 minutes two times a week to increase muscle, which burns more calories.

She has done several studies that show the many health benefits of physical activity and is a strong supporter of trying to do at least three hours of moderate exercise a week.

To do that, Manson advises wearing a pedometer and aiming for walking 10,000 steps, or about 4 or 5 miles a day. About half of those steps can be done through a structured activity like taking a brisk walk a couple of times a day, and the others can come from climbing stairs or walking across the mall.

"Despite all the technological advances in modern medicine, regular physical activity is as close as we've come to a magic bullet for good health," Manson says. "So, find activities you enjoy and do them."