Upon running out of food, your active barracks will receive damage until they are below level 1 and no longer consume food. Deactivate all barracks you can, to slow food consumption.

Running out of food will also begin to damage province morale. If not properly handled, and very quickly, at that, this will spiral out of control as provinces produce less resources with lower morale. Less food being produced will feed into the problem of: Not having enough food.

No they will not.

Short version: You're f---ed, as they say in British English.

Longer version: Your province morale will decline throughout your empire, provinces with already low morale may rebel and defect to other players. Worse yet, declining province morale will lead to declining resource production ---- including less food produced ---- which will make your province morale even worse. This is what we poetically call the "death spiral."

Bottom line: Stop producing new units. Get your food production up. Reinforce food provinces with marginal morale with garrison units whose strength is greater than 7 strength points. Add fortifications to improve morale and increase food production in those provinces with marginal morale.

There are several good how-to threads on increasing production, including one by me which is "pinned" at the top of the forum's Questions and Answers section.

Good luck.

Rule number one: Never run out of food. Actually food shortage occurs before you run out of food. I have seen it at about 8 hours of food remaining.

Food shortage is a severe morale penalty. It can be as much as -30 in the daily morale calculations and affects all of your provinces.
You can also get resource shortage if you are short of non-food resources.
if not corrected, it can lead to higher chances of revolts as provinces drop to 25 and below.

The food shortage morale factor varies by province.

Things very bad your morale will go down and your armies will sufer but here are some tips first deactivate all your barracks sell some surplus resources and buy food from the money and build infrastructure in all of your food province

you can’t deactivate a barracks , barracks don’t have a upkeep cost now . Also this is a 3 years old threat.

You can do that in classic version