I usually lose weight while I'm on trips, mostly because I fast a lot, but there are many temptations you have to avoid. They pile on a lot crap and junk food out of some of the stations and you get real bored flying over the ocean with out much to do. I've done a lot of international commercial deadheads and with those it's very easy to feel like you are going on vacation and something and start pounding down the free drinks and food in the lounges and flights.