The issue of alcohol and weight-loss is complex, there doesn't seem to be a simple calculation to deduce how it affects the system. The problem is that alcohol is metabolised directly by the liver as a preferred source of energy using a completely different chemical process to that for digesting carbohydrate. The normal view is that this "pauses" your low-carb diet, meaning that carbs you eat on the same day are more likely to cause weight gain. The advantage of alcohol rather than excess carbs is that it doesn't seem to boot you out of ketosis, meaning that you can get directly back to losing weight the next day. I tend to drink spirits with low-carb mixers but only once a week and even this certainly seems to slow the weight loss compared to the several months I was dry.