Researchers used cross-sectional data from the National Health and Nutrition Examination Survey (NHANES) and studied 2,178 young adults, aged 20 to 49 years, with different levels of fitness. All participants had blood work-ups for total cholesterol (TC), high-density lipoprotein cholesterol (HDL-C), glucose, insulin, fibrinogen, and homocysteine levels. Blood pressure, height, and weight were recorded using standard protocols. Fitness categories, based on the norms for age and sex, were used to define low, moderate, and high levels of cardiovascular fitness.

The researchers looked at the relationship between BMI level and cardiovascular fitness level to determine whether it is better to be fat and fit or thin and unfit.

While this was a cross-sectional study that measured risk factors at one time point, the findings show that for most markers it was better to be thin and fit than fat and unfit, Dr. Eaton said. "High fitness and normal BMI subjects had the best cardiovascular disease risk factors. Those who were obese and unfit had the worst cardiovascular risk factors."

But, he noted, the study results also suggest that it is better to be normal weight and unfit than obese and fit.

"This study adds to the dialogue that weight is more important than fitness." "If you are overweight it is better to get down to normal weight than be overweight and fit."

Robert Eckel, MD, president of the American Heart Association and professor of medicine at the University of Colorado Health Science Center in Denver said that, “This study raises important questions as to whether or not being fat and fit is okay." "The biomarker report here is not as favorable as that previously reported.

"Being both normal weight and fit remain the best recommendation for prevention of cardiovascular disease and diabetes," he added.