For years, the problem had researchers flummoxed — why, in weight loss trials that require participants to diet and exercise, did Black women have consistently less dramatic results than their White counterparts? Now, one group of researchers purports to have the answer: it's not that Black women aren't trying; it's that it's actually physically more difficult for them to lose weight.

New research published today in the International Journal of Obesity indicates that when it comes to weight loss, metabolic differences between Black and White women are at fault for observed differences in the results that the two groups achieve from diet and exercise. Previously, researchers speculated that maybe Black women simply weren't trying as hard as their White counterparts.

But now it seems that the problem is that Black women have to try harder to get the same results as White women, because Black women's bodies metabolize fewer calories when they exercise.

The researchers found that the African-American women lost about seven pounds fewer than the Caucasian women, even though their starting body mass index, or BMI, measures were comparable and they followed as closely to the calorie restriction and activity prescriptions. But the African-American women had lower resting metabolic rates and expended less energy daily than the other group.