Some genes – located in specific areas of the chromosomes – play an important role in determining how much alcohol it takes for a person to feel the effects. Recent studies show that as much as 50% of the risk of alcohol dependence is determined by genetic factors.
Slow response to alcohol. People who need a large quantity of alcohol in order to feel the effects are at greater risk of developing dependence. Men and women who tend not to feel drunk should therefore pay closer attention and refrain from unlimited drinking.
Quick response to alcohol. Some people have to be careful for the opposite reason. These are the drinkers who feel drunk and lose control over their bodies sooner than the average person.
It is not uncommon for such people to have a family member with a serious drinking problem.
Like those who are slow to respond to alcohol, people who are quick to respond must be more careful than the average drinker. They should drink less than the amount recommended here in order to avoid social gaffes and accidents.
Our recommendations are for men and women of average weight and height. But we know that blood alcohol level is basically the amount of alcohol you absorb divided by the amount of water present in your body. Thus, the less water you have in your body, the higher your blood alcohol level will be.
People whose weight is below average and those with a high percentage of body fat must be very careful and drink less than the low-risk recommendations for the average person.
Low body weight. If your weight is below average, your body will also have a lower-than-average water content, which means that, all other things being equal, you will have a higher blood alcohol level than the average person who drinks the same amount. If this sounds like you, be careful!
High body fat. The same warning applies if you have a higher-than-average body fat percentage. Given two people who weigh the same, where one is well muscled and the other is overweight with a high body fat percentage, the one with the high body fat will feel the effects of alcohol more than the one with all the muscle. That’s because fatty tissue does not contain much water.
Young adults. The low-risk drinking guidelines are designed for adults. Teens who wish to drink should be careful and drink less than the recommended amounts.
In fact, teenagers can’t handle alcohol as well as adults. They often weigh less and have less water in their bodies to dilute the alcohol. Also, compared to adults, young people have fewer of the enzymes that help the liver eliminate alcohol.
Furthermore, the adolescent brain is more vulnerable to damage by alcohol. Recent studies in neuroscience and child psychiatry show that the brain is not really fully developed until after the age of 20. Teens are therefore at greater risk when they drink because alcohol inhibits the development of some parts of the brain.
Older people. As people age, their kidneys, liver, cardiovascular system and brain undergo changes. Some of these changes make the elimination of alcohol less efficient, while others make people more sensitive to the effects of alcohol.
Older people tend to have a higher body fat percentage than younger adults and less water in their bodies. An older person will therefore have a higher blood alcohol level than a younger person who drinks the same amount.
Also, because of their increased physiological vulnerability and the fact that many of them take prescription drugs, some older people should drink less than the low-risk guidelines for the general adult population.