More Sweat, More Fiber

Feeling guilty about not getting the half hour of daily exercise the surgeon general recommends? Now you can feel twice as guilty. Last week the Institute of Medicine, a division of the National Academy of Sciences, upped the target to a full hour. But don't panic. A little exercise still goes a long way.

The IOM didn't set out to devise an exercise guideline. The panel's assignment was to come up with dietary recommendations for fat, carbohydrates and protein. The exercise suggestion evolved as a way of helping people maintain a healthy body weight in the land of supersized meals. Nearly two dozen studies on metabolism show that people with stable body weights get at least an hour's cumulative exercise a day through workouts and everyday activities like climbing stairs.

The group's dietary recommendations were progressive in their own ways. They allowed more leeway than before on fats, carbs and protein, noting that healthy diets can vary widely in the amount of each they include. The report also drew distinctions between desirable and undesirable fats. (Hint: limit the saturated ones and avoid partially hydrogenated vegetable oils.) The most radical move was to set fiber guidelines for the first time. The panel recommended 38 grams a day for men and 25 for women--or about twice the amount the average American eats. It sounds like a lot, but it's doable. "You can get there just by eating the fruits and vegetables we've been telling people to eat all along," says nutritionist Joanne Lupton of Texas A&M University, who served as chair of the panel.

An hour of exercise may not sound so doable. But that's OK, because 30 minutes of exercise still confers great benefits. Just last week The New England Journal of Medicine published a study of 74,000 women, who slashed their risks of heart disease by 30 to 40 percent with only half an hour of brisk walking a day. "Physical activity is as close to a magic bullet for good health as we've got," says Dr. JoAnn Manson of Harvard's Brigham & Women's Hospital, lead investigator in the study. Sixty minutes a day was even better, but not by much. "We can literally walk away from many chronic diseases," she says. Just a little shoe leather will do it.