Personal responsibility. If we would take responsibility for our actions, eat better, exercise more, drink less alcohol, and don't abuse drugs or smoke, we could cut a significant chunk out of our total healthcare expenses.
If you have a body mass index (BMI) of over 40 (morbid obesity), there is a good chance you are diabetic, hypertensive, have problems with your cholesterol, have obstructive sleep apnea, are at risk for coronary artery disease and are probably also hypothyroid. Smoke, and your chances of having these increases plus you will eventually have COPD or emphysema. All of these conditions require doctor visits, often result in hospitalizations and almost certainly require several prescriptions to manage.