"The impacts of preventive medicine are often overstated"

Ezra Klein says practicing preventive medicine is difficult:

Meanwhile, the reason doctors are constantly prescribing statins along with admonitions to exercise and eat better is because using public policy to change diet and exercise habits is really, really, hard, unless you’re prepared to be very heavy-handed (i.e, outlawing trans fats in restaurants, setting portion limits, etc). Indeed, part of the problem with preventive health measures is that, rather often, they don’t work very well.