There are many factors to consider. One very important factor is weight. A person who is substantially larger (more body weight) than another person may be able to consume more alcohol before getting intoxicated. Another factor to consider is previous drinking habits. Say for example there are two people - one of them drinks regularly and the other doesn't. The person who never drinks may get intoxicated quicker because they have never had alcohol before. In addition, health of the individual matters. A person who has a liver that is severely damaged may get intoxicated very quickly because the liver is unable to filter properly.
I'm certainly no scientist, but this isn't really as puzzling as it seems. Several factors contribute to how quickly alcohol is absorbed into the system.
The first is body size (weight). Let's face it, anything absorbed into the bloodstream is going to move through a smaller person's body much more quickly than that of a larger person.
The second is absorption. If someone is drinking on an empty stomach, there's nothing to absorb any of the alcohol, whereas eating something periodically will help absorb some of the alcohol before it hits the bloodstream.
The third is tolerance. I really don't know how this works, but I know it's true. Just as different people have different levels of pain tolerance, they can have differing levels of alcohol tolerance. The first two are somewhat knowable and can be accounted for by someone who chooses to drink. This is kind of the unknown factor, and it can change over time.
Hope that helps. I'll be anxious to see if anyone has a more scientific approach to your question!
Several factors influence how the body metabolizes alcohol. A few include the following:
1. What is the body weight of the person? Generally, more body weight means more alcohol has to be ingested to become intoxicated.
2. Has the person eaten lately? Generally, if a meal has been consumed recently, it takes more alcohol to become intoxicated.
3. Is the person accustomed to drinking alcohol? If one only drinks periodically, intoxication usually comes faster.
4. Does the person have a healthy liver? Liver disease slows metabolism of alcohol.
5. What was the mental state of the person drinking the alcohol? Generally, if the person was in a good mood before they started drinking, they become intoxicated sooner.