Moderate Exercise Not Enough to Prevent or Reverse Obesity

Publication on the use of physical activity to prevent and treat obesity and its comorbidities

The American College of Sports Medicine (ACSM) convened a conference, "Physical Activity in the Prevention and Treatment of Obesity and Its Co-Morbidities," on February 4–6, 1999, in Indianapolis, Ind.

The conference focused on the role of physical activity in obesity and medical conditions associated with it, such as cardiovascular disease, and published the conference proceedings. (See Appendix 1 for a list of conference cosponsors.)

ACSM is an association of 17,000 physicians, scientists and educators who have a professional interest in sports medicine and exercise science.

Twenty-four experts presented research papers and presentations from the perspectives of current evidence and research issues. A consensus panel (see Appendix 2 for panel members) composed of six experts in nutrition, epidemiology, medicine and sports and exercise science reviewed the evidence presented and formulated a consensus statement on the role of physical activity in obesity.

Key Results

The College's official journal, Medicine & Science in Sports & Exercise, published the papers presented at the conference and consensus statement as a supplement, which is available online. Papers covered the extent of the obesity problem, the role of physical activity in the prevention and treatment of obesity and obesity-related conditions, and other topics.

Key Findings

The Consensus Panel concluded that:

  • The prevalence of obesity is alarmingly high and increasing in the United States. More than half of the population (54.9 percent) is overweight or obese. Obesity is more common in African-American women, Mexican-American men and women, and people who are less educated or have lower incomes, than in other groups.
  • Physical inactivity is common among large numbers of high school students. Two-thirds (63.8 percent) of high school students report vigorous activity three or more days weekly. Physical activity was higher among boys and, whites, and decreased with advancing grade.
  • Less than a third (27.7 percent) of adults achieve moderate or vigorous levels of activity. Almost 30 percent report no regular physical activity outside of their work. Gender differences are less pronounced among adults than among youth.
  • The direct costs of physical inactivity are estimated to be $24 billion a year, or 2.4 percent of U.S. health care expenditures. Physical inactivity and obesity combined account for 9.4 percent of national health care expenditures.
  • The problems of overweight and obesity cannot be solved solely by instituting regimens of moderate exercise in the general population. The increase in energy expenditure from moderate exercise is insufficient to completely forestall weight gain with advancing age or reverse existing overweight or obesity.
  • "Evidence suggests that a high level of physical activity can aid weight control either by improving the matching of food intake to energy expenditure or by raising expenditure so that it is difficult for people to eat themselves into a positive energy balance."
  • Increased physical activity appears to have independent beneficial effects on medical conditions that accompany obesity, including diabetes and high cholesterol.

Key Recommendations

The Consensus Panel noted that a number of research needs remain, including the following:

  • Researchers need improved methods of measuring physical activity and energy intake that are appropriate for population-based observational studies. Motion sensors appear to provide a reliable assessment of patterns of physical activity, but more study is needed. Questionnaires and food diaries offer notably poor measures of nutrient and energy intake.
  • The fields of physical activity and exercise physiology are rich in observational studies that examine people and various characteristics at discrete moments in time. They are lacking in randomized controlled trials, which randomly assign participants to a treatment or comparison (control) group to assess the effectiveness of a given treatment or intervention.
  • If the results of randomized controlled trials are to be convincing to the medical community, they must have sufficient sample size, duration and statistical power to yield a definitive result. The experimental groups should contain women, who have not been included in many previous studies, as well as men.


The Robert Wood Johnson Foundation (RWJF) provided $45,000 in grant support for the effort.