Scientists want to use them to find cures for such debilitating illness as Parkinson's, cancer and diabetes.

Diabetes is an especially costly disease: costly for societies, costly in terms of chronic care, and extremely costly in terms of hospital bills for well-known complications.

According to Gerald Shulman, a cellular and molecular physiologist at Yale University School of Medicine in New Haven, Conn., exercising may prevent and even reverse type 2 diabetes.