They found that people who added an hour of mild exercise or half an hour of moderate exercise per week had increased levels of HDL cholesterol, which is good for the heart.
Increased exercise also produced significant decreases in harmful triglycerides, but only in Caucasians.
It also improved levels of LDL, or bad cholesterol, in women, but not in men.
And exercise brought total cholesterol levels down, but only in Black women.
Researchers attribute some of the findings to hormonal and genetic differences.
The findings are published on the August issue of the Journal of Lipid Research.