One of the most eye-opening aspects of parenthood for me has been how socially ingrained it is for parents to be coercive and controlling about food access in the name of manners. Like, scientifically, we know that kids have much smaller stomachs than adults, and also much faster metabolisms. That makes sense! They're growing! And we also know, scientifically, that kids have different palates than adults - that bitter flavours are much more unpleasant for most toddlers, for instance, and that certain kids have strong sensory aversions to certain textures or tastes. This latter point is also true of adults, too - and it's completely fair!
But you would never demand that an adult clear their plate once they said they were full, or shame them for their inability to finish because they had a sandwich earlier. You wouldn't force them to eat every part of an unfamiliar meal they ordered at a restaurant that they turned out not to like, or tell them that they didn't get to have a mid-morning snack as punishment for not having eaten breakfast. And yet it's considered completely normal to do this to children - especially very small children - whose bodies constantly want fuel.
Which isn't to say it's pointless to teach kids manners around food and mealtimes - it's not! How to sit at a table, how to use a knife and fork, how to behave at a restaurant, how to politely ask for seconds or express that you're full (I've had an elegant sufficiency, was my grandmother's delightful go-to phrase), how to join in the conversation once you're done with your food, how to make a good faith attempt at trying unfamiliar dishes, how to broaden your palate as you get older, how to behave as a guest at someone else's table - all of this is important to learn!
But instead of this, what a lot of parents actually do - and most often because they themselves were raised with it - is treat food access as a test of obedience. A child who asks for a snack is whiny, because you just had breakfast!, even though it's developmentally better for a child to eat multiple small meals throughout the day than three big ones. A child who refuses a given food is picky, because you should just eat what you're given!, even though most adults would never extend this same attitude to themselves. A child who eats three square meals a day and still wants more is greedy, because you've already had enough!, even though we'd consider it wholly normal for an adult - and especially a physically active adult - to want extra.
And at the same time, once kids are old enough to feed themselves, they're often discouraged from doing so, their hunger treated as a shameful inconvenience. Sure, if a particular food is expensive, difficult to acquire, needed for a particular dish that someone is planning to cook or belongs to a specific household member, then it makes sense to say, "hey, you can only have X if you ask, for Y reason," because that's about teaching responsibility and courtesy, not punishing hunger. It's also fair to say that certain foods, like ice cream, are only for dessert, or require permission, because kids need help learning restraint. And once they can write, you should teach them that, if they take the last of something, they should put it on the shopping list so you know to get more.
But a lot of people still just... act annoyed that their kids are hungry, and particularly when that hunger - as is developmentally normal! - falls outside of allotted mealtimes. Because they grew up being punished for being hungry, and so it's built into their bones that food-seeking behaviour is somehow inherently rude, when eating when you're hungry is actually one of the healthiest things we can do.
