It is possible to be fat and fit at the same time, a surprising new study has revealed. In the first national study of its kind, researchers found that 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.

Researchers from the University of Michigan also found that close to a quarter of U.S. adults in the recommended-weight range had risk factors for heart disease or diabetes. That means some 16 million of them are at risk for heart problems, the study said.

In one study, scientists analyzed nationally representative government surveys involving 5,440 people age 20 and over between 1999 and 2004. Most people in the study led sedentary lives.

The new study, appearing in Monday's Archives of Internal Medicine, found that risk factors for heart problems were generally more common in older people, smokers and inactive people. Among obese people who were 50 to 64, just 20 percent were considered healthy compared with half of younger obese people.

Authors found that there was difference between the results of overweight and obese people. The ones in the "healthy" category mostly had smaller waists than those with at least two risk factors.

Researchers found that people with larger waists and bulging stomachs, however, had high blood pressure, cholesterol and other factors because fat tissue releases hormones and other substances that affect the body mechanism.