We were trying to stand our ground and get our picky eaters (2 year old twins) to eat the meals their parents are presenting them.
We stopped giving them snacks in between meals. If they didn't eat what was offered, we didn't offer their preferences; instead, we covered the food and re-offered it to them later.
Predictably, several tantrums resulted. Everything happened, from angrily knocking their food off the table to throwing such an overblown red-faced tantrum that they tired themselves to sleep for the night after still refusing to eat what was offered. This "standoffish" state went on for about a week, and we noticed that they'd rather resort to having a liquid diet (juice and milk) even if it wasn't filling them up much. They refuse to drink water.
We gave up (temporarily) and let them return to their normal, sugar-based preferences. We weren't prepared for the degree of tantrums, lasting more than a few days, and the twins were not more willing to eat once the tantrums were over. They were just continuously irritable.
They understand what we want them to do, but are adamant about not doing it, even if they are fatigued.
We don't want to struggle with picky eaters when they're older and even harder to correct, but we're not sure what to do.