Dancers take part in open auditions to become a Radio City Rockette for the annual 'Radio City Christmas Spectacular' show in New York City, May 6, 2008. [Agencies]

It may be possible to be both fat and healthy, researchers reported on Monday, for at least half of overweight adults, and close to a third of obese men and women, have normal blood pressure, cholesterol and other measures of heart health.

And being lean does not necessarily protect people, either. Close to a quarter of normal-weight U.S. adults in one study had risk factors for heart disease or diabetes.

"We really don't know as much about obesity as we think we do," Judith Wylie-Rosett of the Albert Einstein College of Medicine in New York, who oversaw the study, said in a telephone interview.

"A considerable proportion of overweight and obese U.S. adults are metabolically healthy, whereas a considerable proportion of normal-weight adults express a clustering of cardiometabolic abnormalities," Wylie-Rosett and Rachel Wildman and colleagues wrote in their report, published in the journal Archives of Internal Medicine.

Wylie-Rosett's team looked at data on 5,440 men and women who were examined and filled out questionnaires for the National Health and Nutritional Examination Surveys between 1999 and 2004. Most did not exercise very much.

They found just over 51 percent of those who were overweight, and 31.7 percent of those who were obese, had healthy levels of cholesterol, blood sugar, blood pressure and other measures linked to heart disease.

These measures have been shown in many other studies to predict heart attacks, strokes, diabetes and other heart disease, although this particular study did not look at whether people suffered any of these problems.

Obese yet Healthy

More than 23 percent of those who were at a healthy weight, as measured by body mass index, had two or more unhealthy readings, the researchers found.