Out of my very limited anecdotal experience (two small children), it mostly relates to how well fed they are: unfortunately, both of our two kids are bad eaters

Out of my very limited anecdotal experience (two small children), it mostly relates to how well fed they are: unfortunately, both of our two kids are bad eaters (the first just wouldn't eat enough, ever, even today at 5yo; the second is just extremely picky but eats plenty of what she likes). The older kid kept waking up in the middle of the night even at 3 yo (not to ask for food, but when we were sure he got stuffed in the evening, never did he wake up). The younger slept through the night at 10 months a few times, but as she gets pickier, those are actually less frequent now at 15 months than back then. I am sure we could train them with some sort of food scarcity approach (this is the only thing there is to eat; now is the only time you can eat) to teach them to eat enough of the food that's there, but that'd take a psychological toll for a few weeks on us that we aren't able/willing to take on.