Yes, I'm well aware of this, eat less, and eat healthier. But I'm not in the same shape that I was in 25 years ago. I'm still held to a height and weight standard by the Army. My days of running are done, I have 117 military jumps, my knees are destroyed, and I have a slight curvature in my spine. I have run 14 miles while wearing a load bearing vest, jungle boots and carrying a M16 w/ a M203. Most of this run was done on fire breaks, meaning that I was running in deep sand. I'm pretty sure that I've proven to myself that I might be just a little tuffer than the average person.
I don't mind walking or doing road marches, but my body has run it's last mile, years ago.
I get it. One of my buddies (10 years older than me) vet, shot knees, etc...
He rode bikes. Like all over the state. Some dudes swim. You do what you can with what you've got to work with. Just don't quit.