Alcohol affects women faster than men because their bodies produce smaller amounts of an enzyme that breaks it down in the stomach. More alcohol therefore passes into a woman's bloodstream, thus rendering them more vulnerable to the short-term effects of alcohol consumption. The effect is more pronounced among alcoholic women, because the stomach apparently stops digesting alcohol at all. The effects are exacerbated by the smaller build of women, the greater amount of fat and less water, and the fluctuating levels of different hormones.
Many factors are important in determining how a particular adult will react to a given dose of alcohol: age, duration of drinking history, nutrition, individual metabolism, or an inherited genetic predisposition related to maternal or paternal drinking behaviour. On average, one drink for an average woman is roughly equivalent to two or more drinks for a man.