"The extent of alcohol's effect on the central nervous system depends on how much is in your blood and how much blood you have. This is because alcohol is distributed through the body by the water in your bloodstream, according to the NIAAA. The more water in your blood, the more diluted the alcohol will be.
Generally, the lower your body weight, the less blood and water you have. So, smaller people usually have a higher ratio of alcohol in their blood if they drink the same amount a heavier person drinks.
For most people, intoxication begins to occur after two to three drinks, but it can occur more quickly, with fewer drinks in a lighter person. Keep in mind that the alcohol content of different types of beer, wine, and distilled spirits can vary a lot."