hearty appetite of a growing child
Refers to the period when a child is growing rapidly and eats a lot. Often used in phrases like 食べ盛りの子ども.
My son is at a growing age with a hearty appetite now, and he asks for seconds at every meal.
In households with growing children who have big appetites, food expenses pile up.
My son is at the growing-appetite age and asks for seconds of rice several times.