There are several physiological reasons why a woman will feel the effects of alcohol more quickly and strongly than a man. Women are often smaller than men, and thus have a smaller volume of blood, so consuming the same amount of alcohol as a larger man will result in a higher BAC. However, even if a man and a woman are the same weight and drink the same amount of alcohol, the woman will still become more intoxicated. This is true for several reasons:

• Women have less water in their bodies than men do—water makes up 52% of a woman’s body, as compared to 61% of a man’s. Therefore, a man’s body can dilute more alcohol than a woman’s body can, and more alcohol will stay in a woman’s body (increasing BAC).
• Women tend to have a higher proportion of body fat than men of the same weight, and this affects how the body processes alcohol. Alcohol can’t be dissolved in fat, so more alcohol becomes concentrated in a woman’s body fluids (like blood), raising her BAC to a higher level than that of a man of similar weight who drinks the same amount of alcohol.
• Compared with men, women have less alcohol dehydrogenase (ADH), an enzyme in the liver and stomach that breaks down alcohol. Because the alcohol in a woman’s body isn’t broken down as efficiently as in a man’s body, more alcohol enters a woman’s bloodstream and her BAC increases.
• Hormonal differences between men and women may also affect alcohol metabolism. During a woman’s menstrual cycle, changes in hormone levels affect the rate at which a woman becomes intoxicated. Alcohol metabolism slows down during the premenstrual phase of a woman’s cycle (right before she gets her period), which causes more alcohol to enter the bloodstream and the woman to get drunker faster. Birth control pills and other medications with estrogen also slow the rate at which women process alcohol.

When men and women drink alcohol at the same rate, regardless of their weight, women will achieve a higher BAC and become more impaired. This is because of physiological differences in body composition, metabolism, and hormones. So girls, don’t try to go beer-for-beer with the guys—they’ve got the biological advantage on this one!

Source: Winchester Hospital