I think you’re right - it is good to children to serve themselves and others too, and eating together as a famiky and having the freedom to serve yourself the amount you want promotes a healthy relationship with food….but the downside of this is that if more than a sensible amount for the meal is put out, it can be easy to take too much. For adults and any children who might want to regularly eat more than they really should, lots of self discipline is needed to not take a second helping on a regular basis. That’s why, not putting out 8 portions- worth (because that’s what was cooked) for 4, isn’t a good idea. It’s just too easy to regularly take more and it becomes the norm.
I don’t think anyone’s suggesting occasionally eating an extra large portion is a problem, but doing it regularly is. And when large quantities are offered it’s easy to do this.
We’ve been on holiday with friends, and of course in a self catering place, we like to have nice food and plenty of it because it’s holiday time. I’ve noticed that the man in the other family will have a plateful like my DH, then he will have a second helping of roughly a similar size and if there is still some left, he will have a third plateful - effectively 3 dinners. If there’s only enough for 2 helpings, that’s what he has ….and isn’t hungry later. And if there isn’t any left for seconds, again he is fine and not hungry later. Because it is there, he will fancy it and eat it. Maybe no problem when it’s happening 10 days out of 14 on holiday, but if you regularly serve huge quantities, it’s easy to keep eating and it becomes the norm to eat vast amounts…and to think nothing of it.
No-one wants to be a killjoy about food, but actually large proportions of the population, including many of us on here are overweight and one contributor is simply that we eat dinners that are too big. Keeping a lid on portion sizes can make a massive difference, without leaving anyone hungry.