“...I was running 6+ miles at a time, 3 times a week. I even did a non stop, running all the way half marathon.”

I knew it! You are WAY better shape than I am. Right now, I cannot run more than a tenth of a mile at a time. I think I have some knee problems. Perhaps I need to build up my muscles there before seriously considering running on a regular basis? I imagine pool time can help. I also been having trouble meeting my calorie targets. So I will run/walk every two days. I still will keep my calorie count up there in what I consume every day. Then I will move the overage of one day to the shortfall of the next day. This will also help my knee situation. I will make this work one way or another. Also, for the time being, I will not walk long distances. I will frst warm up for a quarter of a mile. I will then walk and run on the running track up to two miles. My goal here is to increase the time that I can remain running.

BTW I weigh 173 pounds today.