My wife and I tend to do long trips, 20 to 30 days on the water.  At the same time we like to eat well, really well, so food prep and planning is an important part of our trip.  As we started getting into longer trips one of the first decisions we made was to get a dehydrator.  With that it is possible to prepare nutritious, gourmet quality meals while at the same time keeping weight and on the ground prep time to a minimum.  We typically package the ingredients for each dinner and pack them in the reverse order.  I’ve become huge into fishing so we count on augmenting our food supply with fresh fish – I typically figure half our dinners will be fish based but of course we carry back up just in case I get skunked.  Breakfasts are typically either home made granola, porridge (with lots of dried fruit and maple syrup) or pancakes (also with fruit and m.s.).  Maple syrup is weight but I’m definitely willing to carry it!  We typically don’t prepare lunch but just have snacks of nuts, dried fruit, chocolate, or pb&j rollups.  Given that we’re out for 3 weeks at a time, our packs are quite manageable to where we can easily double portage without busting our butts.  
Meal prep and planning is the point, before our trip, where me and my wife start getting into it together (I start planning our next trip pretty much from the moment the last one ends whereas my wife doesn’t give it much thought until we actually start talking about what we’re going to eat, usually 3 or 4 weeks before we take off.)  
Last year I lost about 15 lbs on our trip (I’m not overweight.)  I think that was due to 2 things.  The first is the level of activity.  Even when we’re not on the move everything in camping requires more effort.  Even getting in and out of our camp chairs takes more.  There is a lot of getting up, sitting down and moving around that I don’t really notice when I’m doing it but when I think about it, it certainly adds up to an active day (and I’m a guy who’s used to working out 2 hours a day in the gym anyway.)  The other thing is that I’m so busy living – you know, fishing, setting up camp, going for a paddle, whatever – that I’m not thinking so much about eating between meals.  Often, at home, I eat because I’m bored or I need something to make me feel better over the course of a work day.  I rarely eat between meals because I’m actually hungry.  When I’m camping, I’m so busy living, really participating in my life, that, outside of mealtime, eating just isn’t on my mind.