Actually, insurance already DOES take into account certain risky behaviors. For instance, most life insurance policies will not pay off if you die skydiving -- unless you have purchased what is called a "rider" for that activity, which increases your premiums accordingly. We could do the same here. If you have a BMI of less than 30, you are standard rate. For every BMI 5 increase, you have to buy a rider at an additional cost. This would work for health insurance as well as life insurance.