Sept. 18, 2002 -- New guidelines calling on Americans to exercise for an hour a day are based on shaky science and incorrectly give the impression that few health benefits are gained from shorter periods of activity, a panel of physical fitness experts said Wednesday.
Speaking at a news conference, officials with the American College of Sports Medicine (ACSM) expressed the concern that sedentary people will be even less inclined to exercise if they believe they must do so for 60 minutes each day to stay healthy. The experts said there are innumerable health benefits to exercising for a minimum of 30 minutes a day, as consensus guidelines published close to a decade ago by the ACSM, the CDC, and the surgeon general recommend.
"The scientific data to support a single recommendation of 60 minutes even for the limited objective of preventing unhealthy weight gain is pretty sparse," said Steve Blair, who authored the 1996 Surgeon General's Report on Physical Activity and Health.
The experts say the evidence is stronger now than a decade ago that 30 minutes of moderate daily exercise can reduce the risk of chronic illnesses linked to physical inactivity. Those illnesses include cardiovascular disease, diabetes, and hypertension, and risk reductions are seen in both normal-weight and overweight people.
The exercise recommendation by the Institute of Medicine (IOM), issued Sept. 5, are part of broader nutritional guidelines. The thousand-page report states that at least 60 minutes of moderate-intensity exercise are needed each day to prevent weight gain and achieve the full health benefits of activity. The IOM is a private organization, so the new recommendations are not federal guidelines.
The ACSM experts agreed that more is generally better when it comes to exercise. But they worry that the new activity guidelines are likely to be perceived as unattainable by many Americans, especially those who are not already exercising.
"Given that there are 40 to 50 million U.S. adults who are sedentary, 30 minutes of moderate intensity physical activity is a good starting point, and this message needs to be reinforced," Blair said.
ACSM president Edward Howley, PhD, agreed, adding that getting inactive people to recognize the benefits of any level of physical exercise is a continuing challenge.
"Our original recommendations indicated that more exercise is better, but there is no question that 30 minutes leads to positive health changes," he said. "Sixty minutes may be an ultimate goal, but to get to 60 you have to get to 30 first."
Doing that may be even easier than most people think. Russell Pate, PhD, who was lead author of the ACSM/CDC activity guidelines, says the evidence increasingly suggests that exercising for as little as 10 minutes at a stretch, three or more times a day, is as beneficial as the same amount of continuous exercise.
Blair says the amount of exercise needed to maintain a healthy weight probably varies from person to person.
"There are two very easy ways to determine whether we are getting enough exercise to prevent unhealthy weight gain. They are called the belt and the bathroom scale," he said. ... "What we want to communicate to the public is that 30 minutes of exercise is doing them a lot of good. It is certainly better than doing nothing."