John Underwood is a trainer of Olympic athletes at the American Athletic Institute.
At the American Athletic Institute, they do a lot of research about how alcohol effects performance, among other things.
The thing John taught that I will never forget: Drinking three or more alcoholic beverages in one sitting can take away 14 days of your gym time.
That's 14 workouts. Gone. Progress deleted.
That's only if you have been working out; imagine what happens if you haven't been working out!
("One Sitting": One evening out/Day of drinking.)