Once You Start To Exercise, You Cannot Stop!

Using data collected from the National Runners' Health Study, Williams found that the impacts of increasing and decreasing vigorous exercise aren't the same among all runners. At distances above 20 miles per week in men and 10 miles per week in women, the pounds gained by running less were about the same as the pounds lost by running more. At these exercise levels, the effects of training and quitting training are comparable, and the weight gains and losses associated with changes in exercise levels are probably reversible.

However, Williams found that people who didn't run as many miles per week face an uphill battle if they want to lose the pounds accumulated during an exercise hiatus. At these less intense levels, an interruption in exercise produces weight gain that is not lost by simply resuming the same exercise regimen.

"At lower mileages, there is asymmetric weight gain and loss from increasing and decreasing exercise, leading to an expected weight gain from an exercise hiatus," says Williams. "In other words, if you stop exercising, you don't get to resume where you left off if you want to lose weight."

Specifically, Williams compared 17,280 men and 5,970 women who decreased their running distance with 4,632 men and 1,953 women who increased their running distance over a 7.7-year period. He found that runners who decreased their distance from five to zero miles per week gained four times as much weight as those who decreased their distance from 25 to 20 miles per week. He also found that people who started running after an exercise layoff didn't lose weight until their mileage exceeded 20 miles per week in men, and 10 miles per week in women.

Williams says his findings suggest that an effective public health policy for preventing weight gain may need to include a strategy to keep physically active people active. His study also underscores the importance of avoiding start-stop exercise patterns. Exercise designed to prevent obesity may fall short of its benefits if the exercise is irregular, seasonal, or often interrupted.

"We are getting fat because we don't exercise sufficiently and consistently. The real solution to the obesity epidemic is getting people to exercise before they think they need it, and to stick with it," says Williams.

"Many scientists attribute the obesity epidemic to excess calories rather than exercise, because dieting has been shown to produce more weight loss than exercise," says Williams. "My findings suggest that calorie intake and body weight may be self regulating in active individuals."

"Asymmetric Weight Gain and Loss From Increasing and Decreasing Exercise" is published in the February 2008 issue of the journal Medicine & Science in Sports and Exercise.

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FACT: U.S. Ranked Last in Preventable Death Rates: The United States ranked last among 19 developed nations in the rate of decline in deaths that are avoidable with effective health care, researchers found. Overall, the amenable mortality rate dropped an average of 16% from 1997 through 2003, but the U.S. rate fell just 4%. If the U.S. had been able to match the average reduction of the top three performers -- France, Japan, and Australia -- there would have been 101,000 fewer deaths per year. In 1997-1998, the U.S. was 14th in amenable mortality among males, with 128.51 deaths per 100,000 population, ranking ahead of Austria (132.17), the United Kingdom (148.62), Finland (150.39), Portugal (153.96), and Ireland (157.57). France had the best rate at 85.87 deaths per 100,000 population. Among females, with 101.59 deaths per 100,000 population, the U.S. also ranked 14th, Japan had the best rate at 62.06 deaths per 100,000 population
Nolte E, McKee M, "Measuring the health of nations: updating an earlier analysis" Health Affairs 2008; 27: 58-71.