When I go back home to visit family, which is generally every 12-18 months, I find I indulge more and wind up eating more crap then I do in my every day life. For me it's because I don't access to the same junk food in England that I do in the States, and even though England does have more then it's fair share of junk, I don't crave it in the same way because I didn't grow up with it.
I get back into my normal habits after heading back to England though and normally have to give my body/stomach a few days to adjust again to the different types of food that I'm eating.
I tend to use my time in the States as a chance to eat the foods I enjoy and do it without guilt. I take that attitude because I know that I won't be able to do it again for a while and I know that I'll get back to my normal eating habits once I'm back home in England.