If I lost 45 pounds over a hike, they'd be rolling me out on a stretcher. I can't imagine doing something like this without having to carry massive amounts of food once I am down about 20 pounds, which I consider the max I could lose before losing strength as well.
I lost 13 pounds this summer in 2 weeks (and we ate well with several 'double meals'), and the end result was a weight I had not been at since I was about 25. Maybe 10 more pounds and muscle mass is going.
This also explains why PCT hikers tend to "binge" on things like 5 quart ice cream buckets. Gotta bulk up in a hurry to be out there this long without running out of fuel.
