Washington, Aug 3 - If you are among the least fit segment of the population, then you face twice the mortality risk of even those who are just a bit more in shape, says a new study.

A research team from Stanford University led by Victor F. Froelicher and Jonathan Myers performed exercise tests and followed more than 4,300 subjects from 1986 to 2006, none of whom had a history of heart disease.

Fitness and physical activity levels were measured using treadmill tests and questionnaires, and mortality rates were tracked during the 20-year study period.

Sandra Mandic from the American College of Sports Medicine (ACSM) and the research team from Stanford analysed the results, and found that the mortality rate for the least-fit individuals was twice that of the second least-fit group, and more than four times the rate of the most-fit group.

The study suggests that reduced recent physical activity, rather than differences in health status, contributes to the striking difference in mortality rates between the least-fit individuals and those who are just a bit more fit.