Ten Steps to Conquering Heart Disease You may already know that heart disease is the No. 1 killer in America, and that factors like obesity increase your risk of developing it. But of all the shocking things you know - or believe you know - about heart disease, here's the statistic that you might find the most eye-opening: 80 percent of all heart disease is preventable. "It's important that everyone understand as much as possible about heart disease prevention, as 80 percent of heart disease can be avoided," says Dr. Martha Grogan, medical editor-in-chief of the new book "Mayo Clinic