One way would be to speed up growing up. via tech or magics such that the poopfactory stage is skipped and the kid is physically and mentally 10 within 2 months. growth slows so that physically 24 takes another year or 3. Aging halts after that as long as properly fed.

Might or might not apply to both boys and girls, with much higher ratio of girls. perhaps certain foods need to be eaten before Y sperm can be made.

To aid learning, memories, skills, common sense, can be passed on like asari/vulcan melds

The desire or need to eat meat might be magically removed somehow before first birthday. but the food or breastmilk is rejected by the body past that.

side effect might be the first two months kids might eat like meme goats.

- from pondering on: Why wait 20 years to eat a meatgirl when magic or tech could skip to the good parts. Also, the social side effects of less dependency and bonding time making people more open to people eating.

- the setting might be a colony world that had one weird scientist dude, a goat, and a fridge full of frozen eggs survive a crash. Mad science with zero oversight was done in the shipwreck. Now its a century later and meatgirls is the norm. Or something.