During the prologue of the game, you have to build a reserve of 40,000 units of food. During the course of the chapter, you'll get two options to ease your struggle.
Seal Colony
You'll discover a seal colony. You'll get a prompt saying something like "oh, we are saved. We can slaughter these seals and have enough food for everyone." Don't do it. Don't build a food district on the seal colony.
Elders' sacrifice
After some time, you'll get another prompt saying elders are volunteering to leave the city, so that food consumption goes down. Your options would be to accept the sacrifice or decline it. You have to decline it.
Tips for getting enough food in time: Ignoring the Seal colony, there are 4 other food sources in prologue. Build food districts on them as soon as possible. Tell citizens to tighten their belt and implement emergency shifts in 3 of the food factories. Your trust score will plummet, but try to recover that by giving scraps back to the citizens. Took me a few tries to finish this.