Whether eating out or at other people's houses, I tried watching what thin people do. They eat what they want and are happy to leave things.
It's not easy, but I try to force myself not always to say yes to food or nibbles. Anything I think is too fattening, I refuse on the basis that I've just eaten; I don't like it; or I'm full up. I've found that people accept these reasons whereas if you say you're dieting they keep on trying to tempt you.
It may be lying but quite frankly I don't care.
Tracey