You're asking, and I'm answering.
I've noticed that on a day after a night of heavy drinking, whether I'm hungover or not, I tend to be ravenously hungry. I know that people joke about "hangover foods," but for me, it's not just craving greasy treats. I actually just feel insatiably hungry. Why is this?
— Hungry and Hungover
To see the answer,
Ah, yes. As if the headache weren't bad enough, you also have to worry about a hangover interfering with your healthy eating habits. Before I started researching this answer, I assumed it had something to do with blood sugar, and indeed, blood sugar takes the blame for postparty hunger pangs.
Alcohol, as we know, is high in carbohydrates, and drinking heavily can temporarily decrease your blood-sugar levels. Basically, alcohol throws your blood sugar out of whack, and your body spends the next day trying to readjust, leading to increased hunger.
Here's what else I've been able to figure out from my research. When you drink, your liver is so busy metabolizing the alcohol that it neglects to produce glucose like it usually does. It's especially bad if you're drinking on an empty stomach, because then the drop in blood sugar is even more dramatic, resulting in ravenous hunger. In addition, drinking inhibits the production of a stimulant called glutamine, so the next day, when you've dropped drinking, your body churns out more glutamine than it needs. The resultant overstimulation may also contribute to increased hunger.