Ever wonder why it is so hard to bulk up at the gym? The reason may be genetic, says a team of Canadian researchers.

The scientists analysed volunteers of European, Chinese, Aboriginal and South Asian descent, and found that even among individuals with the same percentage of body fat, South Asians have a lower percentage of skeletal muscle, one of the body’s main muscle groups and the one responsible for all voluntary actions.

The difference in lean muscle mass may be why Indians are more likely than other ethnic groups to develop diabetes and cardiovascular disease, said the researchers. The study is the first to look at ethnic differences in muscle mass as a potential reason for disease risk.

“In general, excess body fat tends to be accompanied by an increase in muscle mass,” said Scott Lear, a researcher at Simon Fraser University in Canada and lead author of the study. “But South Asians had significantly less lean mass than each of the three other groups.”

The researchers found that South Asian men had at least 3 kg less of skeletal muscle than Chinese and European men. South Asian women also had less muscle mass than their counterparts of other ethnicities — by at least 2 kg.

The findings will appear

in the Journal of Clinical Endocrinology and Metabolism in December.