The findings suggest that physical-activity guidelines may need to be changed to take people's ethnicity into account, the University of Glasgow researchers said.
The researchers measured blood sugar levels, insulin resistance and other diabetes risk factors in 100 South Asian and 100 white men, aged 40 to 70, without diabetes. The men's physical-fitness levels were measured using a treadmill test and their body size and body fat were calculated.
Lower fitness levels and greater body fat in South Asian men explained more than 80 percent of their increased insulin resistance compared to white men, the researchers concluded in the study, which was published in the June 27 issue of the journal Diabetologia.
The study also found that lower fitness levels among South Asian men could not be explained simply by lower activity levels. The South Asian men had lower fitness levels than white men at all levels of physical activity, which suggests natural differences in body makeup, the researchers said.
"The fact that South Asians' increased insulin resistance and blood sugar levels are strongly associated with their lower fitness levels, and that increasing physical activity is the only way to increase fitness, suggests that South Asians may need to engage in greater levels of physical activity than Europeans to achieve the same levels of fitness and minimize their diabetes risk," study co-leader Dr. Jason Gill said in a journal news release.
"This has potential implications for physical activity guidance, which, at present, does not take ethnicity into account," study co-leader and professor Naveed Sattar said in the news release.
The U.S. Centers for Disease Control and Prevention outlines the benefits of physical activity.