There is absolutely nothing that gets you in shape like backpacking. I usually lose a lot of weight when camping, but I ate constantly over the last trek and am feeling the same up I do when I manage to string consecutive weeks of exercise together. Went and played basketball yesterday, 2-on-2, make-it-take-it, first to five. The kid I was playing with and I went about 10-1. Would let the other team just run the score up to 4-0 because I knew we could get a stop and score 5 lay-ups in a row, effortlessly.
Seriously, there's a reason hiking hurts so much. It's worth it.