Never mind what the bathroom scales are saying and take a brisk walk: That's the message that emerges from a new study that shows that, when it comes to heart health, it's more important to be active than thin.
The research, conducted exclusively on women, found that those who were fittest were least likely to have clogged arteries, had the fewest heart attacks and had far fewer risk factors for cardiovascular disease. The same associations did not hold true based on women's weight, or body mass index. (BMI is an approximation of body fat.)
"Lack of physical fitness is a stronger risk factor for developing heart disease than being overweight or obese," said Timothy Wessel, a cardiologist at the University of Florida College of Medicine in Gainesville, Fla.
He said the link between BMI and heart disease remains unclear, particularly in women. Dr. Wessel said the problem is that most obesity studies have not adequately measured physical activity and many studies of physical fitness have excluded women with known or suspected coronary heart disease.
The research, published in today's edition of the Journal of the American Medical Association, was conducted on 906 women who were prescribed a coronary angiography -- a test that measures blockages in the arteries of the heart. Practically speaking, that meant many already had a number of risk factors for cardiovascular disease.
The vast majority of the women in the study, 76 per cent, were overweight or obese and just over 70 per cent were virtually sedentary. Their average age was 58.
During the four-year study period, 68 of the women died and 455 suffered a heart attack or stroke.
When the data were analyzed by categories of weight and activity, women who were active, even moderately, turned out to be far less likely to develop heart problems than the sedentary women, regardless of how much they weighed. (The fitness of the participants in the study was judged based on a questionnaire that estimated their daily energy expenditure.)
While the researchers were careful not to say that being overweight or obese is desirable, they stressed that it is important to be active regardless of how much you weigh. This is true even for people with serious heart disease, such as the women involved in the study.
"Increased physical therapy seems to be an ideal therapy for coronary heart disease," Dr. Wessel said. He said that physicians who are treating patients for heart disease -- and its prevention -- should be sure to stress physical activity more than weight loss.
A second, unrelated study also published in JAMA, offered seemingly contradictory results. It found that weight, rather than fitness, was the best predictor of women developing Type 2 diabetes.
The study, conducted by Amy Weinstein and a group of researchers at Brigham and Women's Hospital in Boston, followed 37,878 women over a seven-year period.
"We observed a modest reduction in the risk of diabetes with increasing physical activity level, compared with a large increase in the risk with increasing BMI," Dr. Weinstein said. The women in the study, however, were generally younger and healthier than those in the heart study.
In a related commentary, published in the same edition of JAMA, Steven Blair of the Cooper Institute in Dallas, said the evidence linking obesity to health problems is indisputable but the role of fitness is equally clear. He said the differences in findings were largely a result of methodology and the groups of women studied.
What is important for the public to retain, Mr. Blair said, is that research has consistently shown that a moderately fit obese person is about half as likely to die of heart disease as an unfit person of normal weight. The Canadian Heart and Stroke Foundation recommends that everyone do the equivalent of 30 minutes of brisk walking daily to be considered moderately active.
Mr. Blair, a well-known fitness guru who always makes light of the fact that he is heavyset, said the "fitness versus fatness" debate is academic and irrelevant to people looking to get healthy.
"Physicians, researchers and policy-makers should spend less energy debating the relative health importance of fitness and obesity and more time focusing on how to get sedentary individuals to become active," Mr. Blair said.
About 59 per cent of adults in Canada are considered inactive, and 48 per cent are overweight.