There is an even stronger version of your argument, one that works without shifting to the same old "you don't need the expensive stuff, just get your life together" advice that already has kind of a bad rep for not fixing depression. You can accept that you cannot inject much more of necessary discipline and motivation into people after they leave school.. and still argue against many types of surgery in mostly the same way: by strictly comparing them to other costly endeavors that could bring about those probably-helpful life changes. Many more people could work towards that "real solution" by benefiting from some other spending.. which merely happens to be cheaper than surgery, while still not being entirely up to them.

Example: My town installed an outdoor "grown-up playground" in the nearby park. Probably cost a little over two complicated surgeries. Already saved 10 people from neglecting upper body workout. Just 10 people having a really low-barrier-of-entry gym available to them whenever walking their dog. I suspect its already been cost-effective. Plus, it is reusable and low-maintenance. Try to beat that in the operating room!

The thing is, the fitness level OP is talkign about is not going to be compatible with the grown up playground sort of activities. You need to get jacked basically. You need to be lifting to failure 3x5ish hitting all muscle groups 2x a week with compound lifts. You should be struggling to go up stairs after working legs.

Working out is good, yes, but you need to actually work the body and make it suffer so that it may actually be damaged enough for high rates of muscle growth. So many people do not do enough because they don't like to push themselves, they take it easy and they end up wasting their time in the gym. Even more true as you get older and natural testosterone levels start declining and limiting your muscle growth.

This is why people end up taking spin classes when they can just do it at home on their own stationary bike. For some people, they need a jockey who will kick their ass along with the peer pressure of a room full of people dumping out sweat.