To think that if you don't like something that someone has made for you

[Pukepukepuke]

It's just as rude to make disugested faces, tut, sigh, push the food around and leave it and go and make yourself something else to eat, (if not more) as to say "I don't like this"

[Asmoto]

Yes. Depending on the circumstances, who had made it, whether it was supposed to be a special occasion etc. I would:

Eat it anyway, and pretend to like it
Pretend not to be very hungry
Politely thank them for cooking, but apologise and say I couldn't eat it and why (e.g. too spicy, too heavy, too salty)