How can i avoid gaining weight in Italy?

So here's the situation. I am leaving in a couple of weeks to go see some family in Italy for about a month, the problem is that gaining weight over there seem inevitable, which is a big disappointment seeing as ive been working really hard to stay fit. I know that gaining weight in Italy is a sure thing for me because i have gain a few pounds and comments on how i got a little chubbier from my last visit. The meals usually consist of typical italian meals ( lots of starch and olive oil ) and are served in ridiculous portions. I know i could just eat little portions but it seems to offend people if i dont eat till im over my stomac's limit. The option of exercising while in italy doesnt seem to work as my time spent in Italy is always spent doing some sort of activity like walking, hicking or swimming. So if anyone has any usefull suggestions please let me know :).