Most of my solo trips are 12-17 days.  I typically lose about 10-12 pounds, but gain it back by Thanksgiving.  I find after longer travel days, I rarely feel like eating a heavy meal.  Sometimes, I almost have to force myself to eat more than I want.  On layover days, I eat more.  I think my weight loss if primarily a change from my normal diet, meaning more protein but a lot less carbs and sugar. 

19 pounds is the most I've ever lost, due to a longer trip and much hotter weather than I usually experience.  I started with a 34 inch waist and end with a 32.  I carried out about 4 days of leftover food (usually I have a day or two leftover).  But as I said before, I feel better and stronger. 

I actually look forward to the weight loss each summer.  I could imagine if I didn't canoe trip, I'd probably be 190 in a couple years.  Today, I'm at 160, right on track to get up to my normal 170 in a few more weeks.   :)