Recent research shows that exercise can keep your bone marrow from turning into fat. Bone marrow cells called mesenchymal stem cells transform into either bone cells, fat cells or occasionally other cells when they receive certain molecular signals. Because of this, they determine the strength and quality of bone; the more fat in the marrow, the less bone.
But studies show that when mesenchymal stem cells are stimulated through exercise, more of them turn into bone. Early research shows that the best results come from workouts in several sessions throughout the day.
According to the New York Times:
"Many questions remain, of course ... Still, one lesson is indisputable. Don't sit still more than you need to ... and don't let your children loll about either."