More Reasons to Exercise

Even fat you don't see can kill you. If you're overweight and diabetic, doctor say, you probably have a fatty liver, which raises your risk of ills that go beyond that organ including heart disease.

But a recent study found that moderate biking, walking, or running three times a week, plus resistance training, trimmed fat in volunteer's livers by as much as 40 percent. "It's an added reason to exercise," says Kerry Stewart, EdD, an exercise physiologist at John Hopkins University.