Jason M. Wallace, and others from The Cooper Institute in Dallas, examined the association between fitness and type 2 diabetes in 4,984 women participating in the Aerobic Center Longitudinal Study (ACLS).

"This study has been going on for more than 30 years. Men were first looked at and now women’s risks were now being looked at.

Participating women were free of diabetes when the study began. Based on how long they could walk on a treadmill, the women were classified as being low fit, moderately fit, or high fit.

Eighty-two women developed diabetes during follow-up. The rate of diabetes was 3.2 percent in the low-fit group, 2.6 percent in the moderately fit group, and less than 1 percent in the high-fit group.

After considering other factors, such as age, weight, and blood sugar levels, "women who were in the highest fitness group were at lower risk for developing diabetes relative to women in a lower fitness category," Wallace said. For example, high-fit women were 70 percent less likely to develop diabetes than low-fit women.

"The clinical implications are obvious," Wallace said. "Physicians need to be prescribing physical activity to their female patients to help prevent the development of diabetes."

"There has been very little (research) done on fitness and the development of diabetes in women," he added. "These results do support what we have found in men, that higher fitness levels protect against the development of diabetes."