[nickfromseattle]

> My weight is stable but each time I go to US for a couple of weeks I bring back 3-5 extra kilos

I live in Spain and visit the US yearly, here are my thoughts:

A) "Being on vacation" and eating / drinking a bit more loosely than I do at home.

B) Significant reduction in walking. In Spain I average 60 minutes/day on the low end, and often at 90-120 minutes/day. In the USA, it's maybe 30 minutes.