Population control is used in the community to ensure that they never run out of food. When Jonas remembers saying he was starving, he recalls the lecture he got about starvation in the community.
He was not starving, it was pointed out. He was hungry. No one in the community was starving, had ever been starving, would ever be starving. To say "starving" was to speak a lie. (p. 70)
No one in the community has ever been starving? Why does the word exist then? Why do they still use it? It turns out, it is not true that no one in the community has ever been starving. Later, when Jonas asks The Giver about it, be explains.
It came from many generations back. Centuries back. The population had gotten so big that hunger was everywhere. Excruciating hunger and starvation. It was followed by warfare." (p. 111)
The community clearly initiated population control as a result of famine. Now, they will never run out of food because the population is limited to two children per family, and there will never be three as long as some Receiver of Memory remembers the memory of starvation.
Lowry, Lois (1993-04-26). The Giver (Newbery Medal Book). Houghton Mifflin Harcourt. Kindle Edition.