Wonderful to hear! Sure there are plenty of reasons and excuses why our culture is overweight/obese, but the main ones are transparent. Enough about that.
The last couple of years it seemed that every time I tried to renew an aerobic exercise schedule I was hit by flu or something just as I was getting over the initial challenge. 6 months ago I tried again and have run about 5 days a week ever since. Next month I turn 47, and to be quite honest you wouldn't guess it to look at me
My Dad had his first stroke when he was but a couple of years older than I am now. Sure I still am "at risk" but I frankly don't care as much about measuring how much time I have left, versus being satisfied with how I'm living now. It doesn't take a trip to the doctor to prove the gain in stamina, general fitness, improved immunity to various illness, mental acuity etc.
Exercise doesn't solve all of your problems, but it does yield results that a lot of us could use, and kudos to you for getting with it!
By the way, I'm currently running about 3 miles per run, not huge, but living on a mountain the terrain is challenging. Indications are that I can notch it up to 4 or 5 miles pretty easily. And yes, it's very true that joint stress brings down a lot of runners. Swimming or speed walking are more sensible in my opinion, but swimming isn't available to me here, and my personal history proves that for me I just am not as satisfied with the rewards of walking/hiking considering the relative expense of time and effort. As long as my health enables me to, I choose running.