How to know if I’m too old/unfit for food service?

I'm going to go against the crowd here and say that a job that gets you out of the cab and moving around is much better for your health. Sitting for hours on end is one of the worst things you can do for your heart, muscles, and joints. If you're already having knee and back problems before you reach 40, your sedentary job probably has something to do with it. I've never done food service, but doing LTL and later, USPS contracting, I was always happy to get off my rear end and pull a pallet jack around for a bit.