Alcohol metabolism is pretty complex, though. Your liver can only process so much at once, so you’re not going to extract all the available energy from it if you’re drinking quickly/heavily, because the body will start excreting the excess acetic acid as urine.
That is, a bottle of wine has ~600 Cal in ethanol alone, but to actually get those calories out of it, you would need to drink it slowly, one glass at a time—you won’t actually get 600 Cal out of it if you drink it in one sitting.
Anecdotally: when I used to drink quite heavily a few years ago, I was consuming 500–1000 Cal of ethanol a day, yet still eating a normal ~2000 Cal diet, with ~2 hours a day of moderate physical activity, and losing weight.
The calories per gram you reference is how much energy you get out of substance from literally setting it on fire.
But how much actual energy is available to the human body is very different. And alcohol specifically is very hard for the human body to efficiently turn into eneegy.
In addition alcohol make the mitochondria more inefficient leading to greater energy usage.
Most studies that add alcohol to animals diet find no change in weight.
A calorie is a unit of measure of energy right? But you can release different amounts of energy depending on the chemical reaction you use.
Well the chemical reaction they use to measure energy in macronutrients is not the same chemical reaction that is used by the human body, they burn it instead. Now for most macronutrients this doesn't matter because the amount of calories released by the human body is pretty close to the amount released by burning.
But this isn't true of ethanol which is very efficiently burned, but very inefficiently consumed by the human body. So the 7 Cal/gram is very misleading.
I'm not sure you can say that about a body in a fasting condition described here: the metabolism shifts may be more significant than default caloric counts.
In particular, note the observation about acetic acid being excreted in urine rather than completing energy metabolism in this Wikipedia write-up, and the resulting massive difference in caloric energy output:
