Heart disease is the No. 1 killer of women in the United States, killing more women than all forms of cancer combined. One in four women die of heart disease, while one in 30 die of breast cancer. Obesity isn’t the biggest risk. According to the Centers for Disease Control and Prevention, 39.5% of Americans are at risk for heart disease because of inactivity. The percentages of U.S. adults with other key risk factors are: obesity, 33.9%; high blood pressure, 30.5%; cigarette smoking, 20.8%; high cholesterol, 15.6%; and diabetes, 10.1%.