More than 65 percent of U.S. adults are overweight, a public health concern, according to background information in the article. "Among obese adults, long-term weight loss and prevention of weight regain have been less than desired," the authors write. "Therefore, there is a need for more effective interventions." Current recommendations prescribe 30 minutes of moderate physical activity on most days of the week, for a total of 150 minutes per week. However, a growing consensus suggests that more exercise may be needed to enhance long-term weight loss.

To calculate the amount of exercise needed, John M. Jakicic, Ph.D., of the University of Pittsburgh, and colleagues enrolled 201 overweight and obese women in a weight loss intervention between 1999 and 2003. All the women were told to eat between 1,200 and 1,500 calories per day. They were then assigned to one of four groups based on physical activity amount (burning 1,000 calories vs. 2,000 calories per week) and intensity (moderate vs. vigorous). Group meetings focusing on strategies for modifying eating and exercise habits, as well telephone calls with the intervention team, also were conducted over the two-year period.

After six months, women in all four groups had lost an average of 8 percent to 10 percent of their initial body weight. However, most were not able to sustain this weight loss. After two years the women's weight was an average of 5 percent lower than their initial weight, with no difference between groups.

The 24.6 percent of individuals who did maintain a loss of 10 percent or more over two years reported performing more physical activity (an average of 1,835 calories per week, or 275 minutes per week over the baseline level of activity) than those who lost less weight. They also completed more telephone calls with the intervention team, engaged in more eating behaviors recommended for weight control and had a lower intake of dietary fat.

"This clarifies the amount of physical activity that should be targeted for achieving and sustaining this magnitude of weight loss, but also demonstrates the difficulty of sustaining this level of physical activity," the authors write. "Research is needed to improve long-term compliance with this targeted level of physical activity. Moreover, continued contact with the intervention staff and the ability to sustain recommended eating behaviors also may be important contributing factors to maintaining a significant weight loss that exceeds 10 percent of initial body weight, which suggests that physical activity does not function independently of these other behaviors."

Note: If no author is given, the source is cited instead.

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