When trying to determine who will live longer, checking out cardiovascular fitness is better than looking at body fat, researchers said.

A study of people over 60 found that those who died during the study period -- which followed people for an average of 12 years -- had lower fitness levels.

Within groups of similar body fat, those who had better cardio ratings were more likely to survive. In most instances, death rates for those with higher fitness levels were less than half of the rates for those who were unfit, the researchers said.

They also found that people who were older or who had other heart risk factors were more likely to die.

The 2,600 people in the study were monitored on a treadmill stress test to determine fitness, and body fat was figured by various measures, including BMI and fat percentages.

"Our data provide further evidence regarding the complex long-term relationship among fitness, body size and survival. It may be possible to reduce all-cause death rates among older adults, including those who are obese, by promoting regular physical activity, such as brisk walking for 30 minutes or more on most days of the week," said Dr. Xuemei Sui of the University of South Carolina.