Pure alcohol itself has a lot of calories in (7 calories per gram, for reference fat has 9 calories per gram), so regardless of the alcoholic drink, you can't avoid calories. Even "light" beers have a lot of calories in - unless they compromise on the alcohol content, which defeats the point. Therefore, with drinking comes calories. You can reduce how many calories you have by having, say, diet coke instead of coke in a mixer or sugar free red bull in jagerbombs, but to be honest it's not going to have a massive effect. A pint of beer has around the same amount of calories (200) as a chocolate bar. People don't think about downing 5 pints, but they would think about eating 5 chocolate bars. It's all about perception - people forget about the calories in liquids. The only way to have a lower-calorie night out is to not drink at all, which is probably not what you want to hear.