How do I deal with my family judging me?

I'm staying with my Grandparents this weekend, and I hate HATE HATE eating with them, because I used to deal with an eating problem, and now all they ever do is patronize me with food!!! Like yesterday, I was watching t.v at their house, and at every commercial, they'd ask, "do you want some pudding, it's sugar-free, and fat free!" and it's not just that, it's their tone of voice and vibes. UHH, and I just had dinner here at my house BECAUSE IM SOO HUNGRY, and if I go over there, if i don't have anything, they'll say I "don't eat!".. and later tonight my cousin is having a surprise Bday party, and I don't eat cake, so if I say I don't want any, people will judge me! What do i do, what do i say back to these people?