TUESDAY, Sept. 7, 2004 (HealthDayNews) -- Obese women can ward off heart disease if they exercise. But they place themselves at a higher risk of diabetes if they don't lose weight.
Conversely, even thin women elevate their risk of heart trouble if they're physically inactive. However, their risk of diabetes remains lower if their thinness is not the result of regular exercise.
Those are the results of a pair of new studies that add to the "fat-but-fit" debate. But it's not a case of either-or, said leaders of both studies, who, incidentally, did not know their reports would appear side by side in the Sept. 8 issue of the Journal of the American Medical Association.
It's best to be both trim and fit, they said. The individual studies show just what you risk when you don't get enough physical activity or put on too much weight -- or both.
"There is a very strong interaction between obesity and level of physical activity," said Dr. Carl J. Pepine, director of cardiovascular medicine at the University of Florida College of Medicine and the leader of one study.
But that study shows that "a lean woman who is not fit has a high risk of cardiovascular disease," Pepine said.
The 906 women in the study underwent coronary angiography, a test of heart artery blockage, because their doctors suspected heart disease. Their workups included measurements of physical activity and of overweight, such as the body mass index and abdominal obesity.
Most of the women were neither thin nor fit. The tests found that 76 percent were overweight, and 70 percent had low functional exercise capacity. Over the next four years, 337 of the women had a first coronary event, such as a heart attack.
Lack of physical activity was a strong predictor of such a problem, but there was no significant association between obesity measurements and cardiovascular risk, the study found. That shows that women who have trouble losing weight can do themselves some good by staying physically active, Pepine said.
"Women who have difficulty losing weight might not have difficulty maintaining their fitness level," he said.
And, Pepine noted, "we're not necessarily talking about high levels of fitness." The finding supports the American Heart Association recommendation of at least 30 minutes of moderate physical activity most days of the week, he said.
The other report was based on nearly 38,000 participants in the ongoing Women's Health Study. It found that both obesity -- defined as a body mass index of 30 or higher (174 pounds for a 5-foot, 4-inch woman) -- and physical inactivity increased the risk of developing diabetes. But the risk of diabetes due to obesity was much higher -- more than nine-fold for an obese woman compared to one of normal weight.
By contrast, the risk of diabetes was no more than 18 percent higher in the least active women, compared to the most active.
"This study showed that obesity has far and away a more important effect on developing adult-onset diabetes," said Dr. J. Michael Gaziano, associate professor of medicine at Brigham and Women's Hospital in Boston and a leader of the study.
He quickly added, "I would not want to underemphasize the importance of physical activity in maintaining proper body weight. But being physically fit is not enough to have an impact on the risk of diabetes. You need to lose weight as well."
The hopeful message is that diabetes is not inevitable for someone who is obese, Gaziano said.
"I have a number of patients who developed early diabetes, got their weight down and exercised, and it went away," he said. "People in the early stages of diabetes can reverse the process by both losing weight and exercising. There is reason to believe that modest changes in exercise and diet can have a big impact."
Another study, by researchers at Children's Memorial Hospital in Chicago, showed how physical activity can make a difference in children. The study of 11,000 girls in kindergarten and first grade found that five hours of physical activity a week -- the amount recommended by the federal government -- could reduce the prevalence of obesity and overweight by 43 percent.
The American Heart Association has advice lifestyle factors that can prevent heart problems.