I'm on a diet aimed at reducing the amount of fat in my body. Reducing fat is my first priority, actually losing weight second. How will drinking hard alcohol (let's say vodka or rum) affect my diet? How bad is it?
The calorific density of alcohol is almost as high as fat, but it is metabolized quite differently.
The body is able to metabolize alcohol in a variety of ways. The enzymes involved in these pathways are found in their highest concentrations in the liver. The liver is able to convert alcohol into fat through at least two metabolic pathways, the process is sometimes referred to as lipogensis. This fat could then be stored in the body's tissues. Fatty liver disease is a result of storage of excessive amounts of fat in the liver itself. However the vast majority of alcohol converted by the liver does not end up as fat but rather as acetate. There is a study, where they examined the metabolic fate of ethanol using spectroscopy. In particular, in their conclusion they remark:
So alcohol is not predominantly converted into fat. However acetate seems to be prioritized as a metabolite when present in the body and therefore is likely to suppress the metabolizing of other energy compounds, such as fat, and lead to an increase in body fat over time.
It is also worth noting that alcohol does raise the metabolic rate somewhat mitigating its calorific content as do certain incidental social factors that may co-inside with your alcohol consumption; dancing all night long for example. That said sleep deprivation can also have a negative effect on body composition...
I'd also disagree that it is impossible to exercise after consuming alcohol. I have personally found the psychological effects of mild intoxication to have their advantages in exercise, although motor skills are impaired for a significant time period (compared to almost all other intoxicants). Testosterone and nutrient absorption are also affected by heavy drinking.
There is probably also an argument to be made for alcohol as a muscle relaxant, but probably not a very strong one, and with respect to low doses.
Alcohol is almost as calorie dense as fat. You will have to exercise harder to burn those calories when drinking alcohol than when eating the same amount of protein or carbs. But it's nearly impossible to exercise after drinking because alcohol impairs motor skills. So undeniably, alcohol will be stored as body fat.
Most alcoholic drinks are just empty calories. They lack any substantial vitamins and minerals. Take a look at the nutritional facts for hard alcohol. It's zeroes across the board. So drinks have no beneficial side effects for your diet.
The bottom line is alcohol will not help you lose fat. It will only get you fatter.