My "long" backpacking is not "power hiking" at all. I keep a moderate pace, go 7-8 miles a day (mostly off trial), stop about 3PM. I am out 10-14 days at a time with a few days in between for the summer. I loose maybe 5 pounds. So my food intake is pretty balanced with my output. I think this is quite different than what you do on the thru-hikes.

I think I have read that for aerobic conditioning, half an hour may be fine, but for weight loss it is better to do 2 hours at a time three times a week vs. one hour six days a week. For some reason duration makes a difference. May be that short duration you just burn the calories from food you have just eaten, whereas, longer duration you are getting calories from stored fat.

As for re-gaining when home, yes that is hard, but it does not invalidate the weight loss you achieve when backpacking. I find that my gaining weight has more to do with holiday feasts than anything around the time I backpack! However you loose weight I feel your goal should be slow but steady weight loss. After all, it probably took you 10 years go get fat. Why not 10 year goal to get back to the baseline.

I feel you can achieve slow steady weight loss with less than heroic measures. Just be consistent. It really has to be a permanent life style change that you actually like. For example I ate nothing but wild game for meat for about 10 years. Then I had to start eating store bought beef. Ugh! It was so greasy - made my belly ache. I do not even like it. Also went pretty much without sugar for a few years. Now I cannot stand to eat a candy bar - sickeningly sweet. Start paying attention to what food makes your belly feel good an hour after. If it is good food, you will not be hungry, feel boated, or sick. I still crave junk. I eat some, feel lousy. The crave satisfaction only lasts minutes. Not worth it. For me, to get to the point where I avoid bad food, I have had to eliminate the bad stuff entirely for 6 months to a year. I guess that is sort of like an alcoholic.

Everyone is different. I am lucky to start out with a nice high metabolism and grew up in a family who grew a huge garden and we loved vegetables and no junk food allowed.

And, if you love to hike, who gives a dang about what others say about it. Just do it. It certainly is doing no harm.