So I've seen three doctors, a nurse-practitioner specializing in sports medicine, nutrition, and weight loss, and a nutritionist, as well as doing a lot of my own research, as I always do. And all have come up with variations of the same answer: I overdid it. Some of them attribute it to the long-term fasting, others to the hardcore training, physical labor, and AT hiking, but it doesn't take a genius to put it together and see that it's all of it together.
I'd heard of "overtraining" of course, having been around gyms and various fitness venues most of my life. But I always thought it was something relatively minor, like, "I overtrained last week, so I'm taking this week off to rest." But apparently, there's an actual thing: Overtraining Syndrome, and in stage 3 (where I am), your body is just completely broken down and in serious distress. This, so I hear, is why serious athletes so often have to just quit, and sometimes never come back.
I've heard of something similar before--guys coming home from long-term internment in POW camps have to spend years in recovery, and very often retire from the military when they get back. Theirs, of course, is much more severe than this, but it's the same species, different degree.
If you want to know how it feels, think of the feeling of weakness you get when you have the flu: how doing something you normally do with ease exhausts you--out of breath after walking up a flight of stairs, or spent after a trip to the grocery store. It's that, but without any of the other flu symptoms.
The only cure, it seems, is rest. I've been told I'm not allowed to try to lose weight until further notice. I've got it stabilized (I had been gaining after the hike), but I have to stay where I am and let my body heal and recover before I go back to trying to lose again. No exercise, except some very mild cardio (i.e., going for casual walks). I fudge a little on that, because there's stuff that just has to get done in the garden, so I use that as my exercise. But I take it easy, and only do a little in a day, a couple of days a week.
It's pretty frustrating. Apparently, it can take months, or even a couple of years for the body to come out of it. But I just have to deal with it, and trust that God is doing what needs to be done in my life.