This video adapted from The Hidden Epidemic: Heart Disease in America examines the environmental factors that decades ago made heart disease the leading killer in America. While its root causes were unknown at that time, today, researchers can trace the problem to changes in the American lifestyle after World War II. Postwar prosperity led to more sedentary lifestyles and fattier diets. And cigarettes, which were introduced to soldiers during the war, became broadly popular. Researchers believe that the epidemic can be reversed if people eat healthier diets, exercise more, and stop smoking.