Children need to get fattened up asap. You see it with your own children….how fat they get off breast milk….to give them best chance of surviving.

A lot of people are metabolically flexible, especially when young, so they can deal with carbs. But once they get to 30s and 40s, start getting fat/beer bellies/fat asses from too many carbs.

As carbs are converted to sugar during digestion => insulin spike => body starts storing fat.

But diet is too dogmatic to discuss usually. Whatever works for you is best.