Correct me if Im wrong, but what I remember from reading was that Alcohol was the first thing the body will metabolize. Even before Carbohydrates. When you drink a ton of alcohol, of course this is metabolized first and carbs/proteins/fats sit in your system.
From my view point, its really the snacking and eating after all the drinking that wrecks havoc on the body. I've quit drinking all together to really tighten up, but when I did drink, I'd drink a few and be sure to just have a protein shake w/ water before bed. Never really had any negative effects on my training.