I lived in peru for a couple years. Every day, I ate more food than any one person should ever eat. I never knew Peruvian food was world-renowned, but when I heard that afterwards it did not surprise me. It was always clean, fresh, and delicious. Somehow, despite my poor eating habits there, I managed to lose a lot of weight and felt amazing. It didn't last long when I got back.
Same thing happened on a smaller scale when we went to Europe last year; food was good, I ate more than I should, but the quality of ingredients and portion sizes was such that I felt great and had even lost some weight again. Come back to the "greatest country in the world" and every meal makes me feel like crap...weird.