Other research has shown that having less body fat reduces diabetes risk and that exercise can help too, but the new study by UCLA scientists suggests a link between higher muscle mass and a lower risk of diabetes.

"Our findings suggest that beyond focusing on losing weight to improve metabolic health, there may be a role for maintaining fitness and building muscle mass," says Preethi Srikanthan, an assistant professor of medicine in the division of endocrinology at UCLA's David Geffen School of Medicine.

For the study, published online Thursday and in the September issue of the Journal of Clinical Endocrinology and Metabolism, researchers analyzed data from 13,644 adults who participated in the National Health and Nutrition Examination Survey III (NHANES III) to determine whether there was a correlation between higher levels of muscle mass and lower levels of insulin resistance, a precursor to diabetes.

After controlling for age, race and other factors, the scientists found that for each 10% increase in the skeletal muscle index — the ratio of muscle mass to total body weight — there was a corresponding 11% reduction in insulin resistance and a 12% decrease in pre-diabetes.

According to the American Diabetes Association, 79 million people in the USA have pre-diabetes, which means their blood glucose levels are higher than normal but not in the diabetes range yet.

The finding that more muscle mass is beneficial is consistent with what's already known about muscle and fat — that they do affect metabolism, says Daniel Rubin, an assistant professor of medicine in the division of Endocrinology at Temple University School of Medicine.

"Extra fat has bad effects, but more muscle has good effects. These data are also consistent with data we see on exercise, that it helps decrease diabetes risk, and that a lack of exercise and weight gain increase risk," Rubin says.

Srikanthan points out that the study was not an intervention, it was observational. In other words, the authors did not look at the effect of different kinds of muscle-building activities on diabetes.

It's difficult to know when looking at a correlational study like this one whether it's just a correlation or an effect, says Duke endocrinologist Susan Spratt.

"Are there other healthy behaviors that tag along with high muscle mass that reduce the risk of diabetes? We don't know from this study that if you increase muscle mass you will decrease insulin resistance, but we can infer that might be the case," Spratt says.

It's a welcome message for patients who have trouble shedding extra pounds, Srikanthan says: "We should consider monitoring improvements in muscle mass in addition to changes in fat."