Like a previous poster, my aching arthritic knees got me into cycling, and eventually into Weight Watchers and yoga. Between the three, I feel much better and I can walk down hills (which was almost impossible). I'm thinner too. It is definitely worth it, but it is not easy. I have food issues, and there is temptation at every turn. Yes, I belong to a CSA and eat organic a lot of the time, but I still struggle with cravings. David Kessler's book The End of Overeating, shed some light on that for me. Apparently humans are programmed to want sugar, fat and salt, things that were rare for millenia, but all to common now, and the multinational corporations are making Big Bucks from our propensity for those three things. Although I still struggle, I'm proof that it is possible to change a lifestyle and develop a desire to exercise, not just because it's "good for me" but because I really want to get out and ride. And I had quite a few years of bad habits behind me when I started.
There are some things a good health system could do, like make WW-style support groups available for less $$$, and make it possible to ride or walk to places. Our town recently acknowleged that it's impossible to safely get to some places people need to be without a car, due to the car-centered planning they did in the past. It's not just distance. There are places where you cannot cross the 6 lane highway. And healthy food should not be more expensive than sugary, fatty, salty junk.