I read that about 75% of healthcare costs go to treating chronic conditions. Chronic conditions aren't really a problem on a national scale until people hit their mid 40s. Then it is all downhill. It is really a question of who pays for healthcare as a person ages.
I've no doubt this is true, but there are several problems here. First, the current system is optimized to get as many people as possible into "chronic" conditions that require daily (insurance-covered) prescription medications. That's the cash cow that's consuming the system, and currently there are no incentives to try to reign in those costs.
Secondly, the notion that it's "all downhill" after you hit 40 is a complete myth. There's no reason that most people can't remain physically fit and healthy (without drugs) for most of their adult lives. We have an epidemic of Type-II diabetes, for example, mainly do to atrocious eating and lifestyle choices that are actively encouraged by both the tellingly-named "Grocery Manufacturers Association" and the Pharmaceutical industry, who supply expensive (read, profitable) treatments for these chronic conditions.
What's needed is a recognition that the patient bears primary responsibility for his or her own health, and that starts with things like not having a diet consisting of junk food, getting off one's butt to move, not smoking, etc. Not something that one can wave a wand to make happen, but you have to start by stopping incentivizing poor lifestyle choices and couple that with real education and getting people to know and understand that they can (often dramatically) improve their quality of life with relatively minor behavioral changes.
Price transparency and real competition in medicine is the other key reform needed. Combining these two is the only way to slay the healthcare cost dragon.