Being fit appears to be far more important than being thin for decreasing the risk of heart disease, while the opposite seems to be the case for diabetes, according to two new studies in women.
One study of more than 900 women with chest pain found that those who were unfit were much more likely to have a heart attack or stroke than those who were overweight. But the other, a study of more than 37,000 healthy nurses, found that being fit did little to reduce the huge risk that overweight women face of developing diabetes.
The new studies, published in today's Journal of the American Medical Association, rekindled an intense debate over the relative risks and benefits of being overweight vs. thin, fit vs. unfit.
"The public is going to throw up its hands in exasperation and say: 'I can't get a straight story from you scientists. You're telling me to lose weight. You're telling me to exercise. You're telling me that it doesn't make any difference if I exercise. You're saying it doesn't make any difference to lose weight,' " said Arthur Frank, an obesity expert at George Washington University. "But no one is really saying that. The real answer is: 'You should do both.' "
The seemingly conflicting findings may be the result of the different diseases and populations of women that were studied, with weight perhaps playing a greater role in diabetes and fitness possibly more important for heart disease, Frank and others said.
"Although closely linked, they are different diseases, and it may be the relative importance of different risk factors will vary between them," said Lawrence J. Cheskin, director of the Johns Hopkins Weight Management Center. "The bottom line still is it would be wisest to assume that both body weight and body fat distribution and fitness are risk factors for both diabetes and heart disease."
With the number of Americans who are overweight and obese increasing rapidly, public health authorities have been warning that the nation is facing a major public health crisis. But some researchers have been arguing that the health risks of being overweight have been exaggerated, and that a growing body of evidence suggests that being sedentary and unfit is a far greater problem.
In the first new study, researchers examined 906 women participating in the Women's Ischemia Syndrome Evaluation (WISE) study.
On average, women who were deemed unfit based on their activity levels were significantly more likely to have blocked arteries at the beginning of the study and to go on to suffer a heart attack, stroke or some other serious cardiovascular problem over the next four years, the researchers found.
Those who were overweight but relatively fit did not have a significantly elevated risk once researchers accounted for other risk factors, such as diabetes, high cholesterol or high blood pressure.
"For this group of women, their fitness level was much more important than their weight," said Timothy R. Wessel of the University of Florida College of Medicine in Gainesville, who led the research. "We wouldn't say your weight doesn't matter -- obesity has been established as a known risk factor for heart disease. But, at least for this group of women, their fitness level mattered a whole lot more."
The findings indicate that people who are concerned about their hearts need to make sure they are physically active, Wessel said.
"You need to be out increasing your fitness level and getting back in shape, not just dropping pounds," Wessel said.
Physical activity and fitness may decrease the risk for heart disease through a variety of mechanisms, including lowering blood pressure and cholesterol and reducing inflammation inside the body, he said.
In the second study, a team led by Amy R. Weinstein of the Beth Israel Deaconess Medical Center in Boston and colleagues studied 37,878 women in the Women's Health Study.
Over an average of seven years, women who were overweight were dramatically more likely to develop diabetes, with their fitness levels appearing to affect that risk only minimally, the researchers found.
"For diabetes, it looks like being fit does not counter the increased risk of being overweight," Weinstein said.
But proponents of the importance of fitness over fatness said the heart study supports emphasizing exercise because it is a much more realistic goal for many people.
"It is far easier to get a fat person fit then it is to get a fat person thin," said Glenn A. Gaesser, a professor of exercise physiology at the University of Virginia. "That is really the bottom line. Trying to lose weight and keep it off is, if not darn near impossible, then close to it."