Alcohol is possibly your best friend in your weight gain quest. Not only are alcoholic beverages high in calories, you are more likely to eat unhealthy food while intoxicated. Think about it. How many times have you hit up Jack in the Box while wasted? There is something about being drunk that makes those 2 tacos for 99¢ even more delicious.
Another positive is you are far less likely to be physically active while hungover after a hard night of drinking. If you are still drunk in the morning, even better!
Best of all, when alcohol enters your blood stream, your body puts everything else on hold because it thinks you are going to die. Removing the alcohol becomes the number one priority. All other metabolic processes (such as building muscle) are paused. The fat gained from alcohol is usually in the visceral form meaning it is stored in your gut, packed in around your organs. It will help you inflate the spare tire.
So keep that BAC high.