best way I've found to stay in shape through the years is just stay consistent with whatever it is you need to do. For some people, running a few times a week will work. They can eat almost anything. For others, running is painful and damaging, so they have to do something else. Running was boring to me, though I still work it in every now and then, especially if I get to run behind a particular brunette I see from time to time here in southside Birmingham....I digress.
Cycling has been a huge benefit to me. No knee, foot, ankle, hip or other kinds of pain at all. I ride about 60-160 miles per week, depending on the time of year it is. Spring, I'm riding 5 days per week. But admittedly, it's very tough to stay consistent. Sometimes, you have to walk away from everything else and consider an investment in your future medical care. Mountain biking might be even better, but you gotta have a trail nearby, and it's a little dangerous at times. No more so than mixing with traffic out on the road, like I do...Another tip.....Really, make better choices with the quick meals. Instead of the oh-so-standard burger and fries and coke, skip the fries. Get water instead of coke. Drink Coke Zero.
One final note: It's really all about calories in, calories out. Consider and track how many cals are in some of the things you eat regularly. Don't cheat, and don't underestimate. Overestimation on what you ate versus underestimating what you need or burned working out will go a long ways. We do the opposite most times. We think running for 30 minutes must have burned off lunch. Not if you ate at McDonald's, honey. Maybe if you ate one nugget. Or one small burger with no fries. Running 30 minutes at a 10 minute mile pace at age 35, like me, burns around 400-500 calories. That's a Big Mac, and that's it. Not the fries, not the super size coke.
Stay consistent. Whatever you do, stay consistent to STAY in shape.