I cannot find the studies now, but I have seen multiple times numbers to the effect that medical interventions/treatments are responsible for 10% of health outcomes. The remaining 90% is determined by diet, exercise, and genetics.

Genetics is out of everyone's control. But the fact that 1/6 of the American economy is focused on that 10% is mind blowing.

The best ways to improve your health are to eat less, eat better, and exercise more.