Actually it's not so much the beer as the snacks that often come with it. Drinking arouses the appetite (to be ahead of the funny guys: yes, not only for food). I can tell from own experience: love to drink beer but don't snack, constant weight (BMI<25) for over 10 years.
And as for the spirits: 1 gram of alcohol contains 7 calories. There are 65 cal in a standard glass of whiskey, about 83 in a small bottle of beer. Only alcohol free spirits have zero carbs. Cheers!