“All mammals gravitate to eating the most energy-dense foods,” David Levitsky, professor of human ecology and nutritional sciences at Cornell University, says. “Fat is the most energy-dense food available.” It’s just that sober, you won’t usually give in to those cravings. But after a night of boozy indulgence, you lose such learned inhibitions as disciplined eating, Levitsky says.
Another explanation involves brain chemistry, specifically a brain chemical called galanin.
William Gruchow, a professor at the University of North Carolina at Greensboro, has studied and written about galanin and its effects on various neurotransmitters. “Galanin increases appetite for fats, and consumption of fat causes more galanin to be produced,” Gruchow said. “Alcohol intake also results in increased galanin production.”