It could be a combination of so many things, but I'm not surprised at all. You sweat a lot during the summer in WDW, walk a ton and eat differently.
I'm pretty health conscious and eat accordingly at home. But when I'm at WDW, all bets are off. I'll still eat a clean "base" of food, but then frankly eat whatever I want on top of that. And boy, do I. Even with all the pig outs I do at Disney, I'll only gain 4 or 5 pounds over the course of 2 weeks. Then after I come home and return to my normal nutrition, those 4-5lbs disappear really fast...and I may even lose a pound or two more. That's because my metabolism has spiked like crazy from all the food I eat on vacation. It also makes me ridiculously hungry for the first week I'm home too....
