The problem with alcohol, in general, is not the consumption but the over-consumption.  It is addictive by nature, both physically, and due to the social implications.  People who do not drink are often encouraged through peer pressure to have a drink.  Social pressure is very difficult to resist.  

Alcohol is not all bad.  With moderation, It has been shown to increase insulin sensitivity, lower your risk of heart disease, lower this risk of some cancers, and reduce your risk of Alzheimer’s Dementia.   With the positives in moderation, excess produces negative effects.  Alcohol has a documented list of negative effects or side effects.  Most of the negative effects sneak up on the user.  The most important one for dieters is that alcohol tends to make people make poor decisions and lower inhibition will result in poor food choices.  The other side-effects include:

Alcohol Side-Effects

Alcohol is a macronutrient but outside of energy, it is pretty much an empty calorie.  Carbohydrates, proteins, and fats are used for other purposes in our bodies, and alcohol is only used for energy and fat deposition.  In fact, it is used first for energy and as long as you have alcohol in your blood, most of your body will only burn the alcohol for energy.  This leaves the rest of the carbohydrates and fats to be stored as fat.  

Alcohol Calories Chart

Above is a chart of alcohol-containing drinks and an estimated calory content.  It is a little unrealistic.  I am not sure the last time I had a 5-ounce margarita.  They usually come in 12, 18, 24, 36, 48, 60, and 72 ounce “portions”.  At 157 calories, that would be over 470 calories for an 18-ounce margarita.  

Reasons to avoid or limit alcohol intake when dieting:  

1. 

   Bar Glasses: The lighting creates a relaxed mood.

   Alcohol is very dense in calories.  Only fat, with nine calories per gram, has more calories per gram.  Alcohol, with seven calories per gram, supplies nearly twice as many calories as protein and carbohydrates (each supplies 4 calories per gram). Most importantly, alcohol is a source of empty calories so you will not get any beneficial vitamins or minerals from it.  Even worse, alcohol-containing drinks often contain lots of carbohydrates and may even contain fat.  In particular, wine and beer both have high carbohydrate content and some mixed drinks are very high in sugar.   For the sake of shock, both a Long Island Ice Tea and Margarita have over 700 calories.  

2. Alcohol can increase your appetite.  Alcohol, unlike the other macronutrients, does not make you feel full, in fact, it makes you hungry[1],[2].  You know what this means.  You will get the munchies and eat foods that will pack on the pounds.  Making the combination of alcohol and a fattening meal your diet’s worst enemy. A Canadian study showed that alcohol consumed before a meal increased caloric intake to a far greater extent than did a carbohydrate drink. Also, researchers from Denmark’s Royal Veterinary and Agricultural University showed that if a group of men our diets worst enemy were given a meal and allowed to eat as much as they wanted, alcohol, rather than a soft drink, would increase the amount of food consumed.
3. Alcohol increases GABA usage while you are awake.  GABA is a brain hormone that is a depressant and it allows you to stay asleep but if you deplete your supply before bedtime, you will be more likely to toss and turn[3].  Sleep is one of the parts of the Performance Triad that will help you be more healthy so excess alcohol is a hindrance to proper health.  
4. Alcohol reduces your supply of essential B Vitamins.  Alcohol increases our usage of thiamine, riboflavin, folate, and B6 and thus results in less energy and motivation.  Both of energy and motivation are essential to a successful diet.  
5. Alcohol suppresses testosterone levels.  Ok, now I have every man’s attention.  Drink 4-8 in a setting may decrease it by up to 23%[4],[5].  Less testosterone leads to more sexual difficulties, longer recoveries and repairs, reduced muscle mass, and increased body fat.  Why yes, it also can result in increased breast tissue in males.  Yes, it will lead to or enlarge your “man boobs.”[6].  
6. Alcohol loosens your inhibitions.  We all remember a poor decision we have made while drinking.  It leads to people driving when they have no business on the road.  It leads to trips to the fast-food drive-through (hopefully as a passenger).  You went from drinking too much to eating too much in a quick second.  In fact, it is well proven that you eat more calories if you drink alcohol with your meal than if you drink a soda[7].
7. Fat takes a backseat to alcohol.  When you have alcohol in your bloodstream, it is metabolized to acetate.  As long as you have acetates in your blood, your body will preferentially use it for energy over fat[8],[9].  When dieting, the last thing you want is to suppress the burning or oxidation of fats.

Recommendations on drinking alcohol while dieting:

1. Moderate your intake.  Unlike popular beliefs, moderation is not 2-4 drinks every day of the week.  If you can’t reduce your intake, you need to avoid alcohol altogether when dieting.  Moderation is 1-2 per set 2-3 days a week.  It is also not a case or 5th of liquor on weekends either.  Even those who have a single drink daily can lose weight[10].
2. 

   Drink Serving Sizes: This si a good reference from the NIH Website.

   Eat first and drink second.  Prefill your stomach.  Have a healthy meal of proteins, healthy fats, and fiber before you go out.  A healthy meal will slow the absorption of alcohol and reduce the chance of overeating.  

3. Plan a snack.  Don’t shop or go to a restaurant with the munchies.  If you keep food nearby, you will be less likely to go grazing.  Have a bag of vegetables with you for a snack.  It will fill you up and make you less likely to stray from the diet.  
4. Know your serving sizes.  If you know a 5-6 ounce mixed drink is a serving, then you can do the mass and figure out that a 60-ounce margarita is 10 servings in one glass.  
5. Avoid drinks loaded with sugar and/or fat.  Some liquors and mixed drinks are very high in calories.  This is especially true when you add a mixer.  One serving of bourbon neat has about 64-80 calories but if you add soda or juice you can triple the calorie count.  Know what in the drink you are drinking and avoid these drinks with high-calorie mixers. 
6. Cut your drinks in half.  If you find that you are having difficulty losing weight, calculate your calorie intake.  Think about halving your intake and the number of days per week that you have alcohol.  
7. Pick a drink with a low-calorie count.  If you like bourbon, have neat or on the rocks.  Try a sugar-free mixer.  If I do not have it neat, I like bourbon with golden peach water from Walmart.  
8. Drink plenty of water.  Alternate drinks containing alcohol with 12 ounces of pure water.  It will keep you hydrated which has been shown to decrease food splurges.  Water is research-proven to help with weight loss.  
9. Don’t skip meals.  Have a meal before you go out.  Like I said above.  Alcohol is not filling so if you skip meals to use your calories for alcohol consumption, you will likely overeat after your cruise with your friends to Taco Bell at 3 AM.  

The three most important things for human performance and this includes successful dieting, are adequate nutrition, exercise, and sleep.  Without these three things, you will be less successful at all three.  Moderate your intake and get all the benefits of alcohol with very limited levels of the negative.