Alcohol and dehydration
Dehydration is another issue you have to watch out for if you choose to drink alcohol while trying to build muscle and work out. Since alcohol acts as a diuretic in the body, unless you are sure to replace the extra fluid with water or another non-alcoholic beverage that doesn’t contain caffeine, your natural water balance will be disrupted.
Dehydration has a number of negative effects on the body, from inducing feelings of fatigue to causing low physical performance, making you feel hungrier (which is especially problematic while dieting), and disrupting the ability of the muscle cells to produce ATP -- which is your primary source of muscular energy.
Alcohol and glycogen synthesis
Aside from ATP, the next source for muscular work is stored muscle glycogen. Unfortunately, though, when you consume alcoholic beverages, alcohol synthesis will take precedence over glycogen synthesis, resulting in decreased stores in the muscle cells.
When you go to do your next workout, your body will have less energy to run on, causing fatigue to set in early.
When your workouts are ended prematurely , you won’t derive as many benefits in terms of increases in strength since the necessary overloading stimulus (which is partly defined through volume of weights lifted) will not be increased.
Alcohol and aerobic ability
If you aren’t as concerned with your strength levels and figure this means alcohol is a safe bet for you, you may want to think again. Even when it comes to aerobic activities, alcohol affects performance.
In this scenario, alcohol can cause an increase in blood pressure throughout the body and a corresponding increase in heart rate.
Since your heart will already be working at an increased rate during aerobic activities, the additional stress from the alcohol will only amplify the heart rate and make the exercise feel harder than it should.
Alcohol and body fat
Finally, the last issue surrounding alcohol consumption is that it contains calories, and these do add up quickly. Typically, you’ll likely find yourself drinking beer, wine or hard liquors, which do contain fewer calories than the fancier, sweeter-tasting cocktails that women often drink, so at least that's an advantage.
Still, at seven calories per gram, after three or four drinks, these calories would equal a good-sized meal. Unless you are going to cut down on food intake in order to make room for these calories (which is rare, as usually you’ll actually find yourself snacking on high-calorie items such as nuts, pizza, wings or nachos), fat gain will result.
Just something I found over a year ago before I started working out, didn't know alcohol could slow or kill your gains! Hope this helps anybody's questions to drinking and workingout.