Does drinking alcohol cause an increase in weight gain?

Depends: Alcohol has a carbohydrate effect & stimulates Insulin release which depresses blood sugar and stimulates hunger. Insulin release also turns off breakdown of fat as a backup energy source in the body. Over time this can lead to increased intake, quick deposition of energy as fat stores and eventual weight gain. The skinny alcoholic exists because they seldom spend money on food.

Yes: Alcohol generally contains a significant number of calories per drink. It is better not to "drink your calories.".

Yes, in several ways: Alcoholics, especially late stage ones, can look emaciated with muscle wasting but alcohol causes overwt and metabolic/nutirional problems commonly. 1) empty calories 2)poorer foods are chosen, bad diet 3) severe nutritional deficiencies contribute to brain, nerve and liver issues 4) alc is a direct toxic poison to many tissues, incl liver leading to poor absorption +"use" of nutrients. Exercise -.