Exercise appears less likely to prevent obesity among black teenage girls than their white peers, a new study shows.

British researchers who gauged the effect of exercise on more than 1,100 girls, aged 12 to 14, surmised that black teen girls may be less sensitive than white teen girls to the effects of physical activity to prevent obesity.

“Higher levels of physical activity were associated with lower risk of obesity among white girls but not among black girls,” wrote study authors James White and Russell Jago.

This is of concern because obesity rates are increasing at a greater rate among black teen girls than other U.S. youths, putting them at greater risk for heart disease, according to background information in the study. Black American girls were 80 percent more likely than white girls to be overweight in 2007-2010, the U.S. Department of Health and Human Services’ Office of Minority Health reported. And about four out of five black American women are overweight or obese.