During the last 100 years Asia has seen a significant shift towards eating much more meat as their prosperity has increased, and that's very 'calorie inefficient'; if you have some chickens or a pig at a farm, then that's often a form of "recycling" various scrap; but factory farmed animals consume huge amounts of crops grown for them that have much more calories than the resulting meat/eggs/dairy/etc.

If your daily meal is mostly rice with some vegetables, then cutting down on production means famine.

If your daily meat is processed meat, then cutting down on production means slaughtering the animal stock and processing the soy/corn/etc for human consumption.

It's also good that in the northern hemisphere, where most people live, we can still choose what crops to prioritize for the 2020 harvest; there's some lock-in with specialized hardware and availability of seed stock, but in general we can adapt quite a lot still.