Panel Urges Hour of Exercise a Day.

Americans need to exercise more — at least an hour a day, twice as much as previously recommended — to maintain their health and a normal body weight, according to new guidelines issued yesterday by the Institute of Medicine, the medical division of the National Academies.

In a thousand-page report, a team of 21 experts suggested for the first time a range of recommended amounts for what are called macronutrients — proteins, fats and carbohydrates — and also included advice on how much dietary fiber and exercise people should strive for to maintain good health. Previous reports over the last 60 years have dealt only with recommended levels of vitamins and minerals.

The panel's recommendations give wide leeway in choosing an acceptable diet. The report said that to meet daily needs for energy and nutrients while minimizing the risk of developing chronic ills like heart disease and diabetes, adults should get 45 percent to 65 percent of their daily calories from carbohydrates. It recommended a maximum of 25 percent of calories from added sugars, 20 percent to 35 percent of calories from fats, and 10 percent to 35 percent of calories from protein. In addition, the panel recommended that adult men 50 and under consume 38 grams of fiber a day and adult women 21 grams a day.

The new guidelines, called the Dietary Reference Intakes, are intended for use by professional nutritionists in private practice, hospitals and schools, as well as by individuals.

Do these recommendations sound difficult on exercise and loose on sugars? They do to me, and apparently they do to this expert.

Dr. Marion Nestle, chairwoman of the department of nutrition and food studies at New York University, called the exercise recommendation "amazing but impractical," given that 60 percent of the population is now totally sedentary.

"I hardly know anyone — and I know a lot of health-conscious people — who exercises an hour a day," Dr. Nestle said. "This creates a lot of tension between what's ideal and what's possible. We know half an hour a day confers substantial benefits. Wouldn't it have been better to say some exercise is better than none, and more is better than some?"

Dr. Nestle said she was also concerned about the panel's recommendation that as much as 25 percent of calories could come from added sugars, the caloric sweeteners added to manufactured foods and beverages like soda, candy, fruit drinks, cakes, cookies, ice cream and other sweets. The 25 percent limit would allow a person who consumes 2,000 calories a day to drink three and a third 12-ounce sodas each day, if soda was that person's only source of added sugars.

"This is a huge amount of added sugars in a country where soft drinks, a major source of sugars in the American diet, are increasingly a factor in the rise in overweight," Dr. Nestle said, adding that most earlier recommendations called for no more than 10 percent of calories from added sugars."

For those interested, the press release can be found here - Report Offers New Eating and Exercise Targets To Reduce Chronic Disease Risk and the entire report is available online - Dietary Reference Intakes for Energy, Carbohydrates, Fiber, Fat, Protein and Amino Acids (Macronutrients) (2002).