Although many women watch the numbers on their scales very closely, that isn't the best way to determine the risk of cardiovascular disease, a new study suggests. Findings published today in the Journal of the American Medical Association indicate that a woman's level of physical activity is a better predictor of future heart health than weight alone is.

Many previous studies have shown that being overweight increases the risk of heart disease using assessments such as waist circumference, waist-hip ratio and body mass index (BMI), a formula that incorporates weight and height. The tendency to focus on weight as a risk factor fails to address the related but more important lack of physical fitness among overweight individuals, remarks C. Noel Bairey Merz of the Cedars-Sinai Medical Center in Los Angeles. In the new work, Merz and his collaborators analyzed data collected from 906 women who participated in an established health study between 1996 and 2000. Forty-one percent of the women were characterized as obese and 76 percent were overweight. Although women weighing more had a greater number of heart problems, the scientists did not detect a correlation between their BMIs or abdominal obesity and the likelihood of coronary artery disease or adverse cardiovascular events. The participants also filled out two questionnaires designed to gauge their physical activity levels; the team determined that low activity scores correlated directly with an increased risk of adverse cardiovascular events.

Our findings suggest that self-reported level of physical activity and functional capacity are more important than weight status or body type for determining cardiovascular risk in women, Merz explains. The current guidelines from the American Heart Association encourage women to participate in 30 minutes of moderate-intensity physical activity most days.