How long would it take for an alcohol tolerant person abstaining from alcohol before he looses the tolerance he has built up and becomes a “lightweight” again.
This is only anecdotal information, but I was just thinking of this the other night. I think I have a pretty good alcohol tolerance; however, it’s not uncommon for me to go a couple of weeks alcohol free, then have a few nights in a row of drinking quite a bit each night.
Even though the amount I drink is pretty much consistent from night to night (on the nights that I do drink), I’ve always noticed the effects more the first night I drink, even if it’s only been about a week since I last drank. If, say, I go for a week without drinking, then drink the same amount both Friday and Saturday, I’ll definitely notice the effects more on Fri. over Sat., generally speaking.
(It’s not so significant a difference that it would be noticable to someone observing me, but I certainly feel the difference; however, that difference I feel may be attributable simply to the power of suggestion).
Another anecdote, I quit drinking around the end of 2003, drank nothing for about a year and a half after, and now drink only occasionally. While before I could drink pretty heavily, now one drink will have me slurring and two will just about put me to sleep.
I misunderstood the OP. I was gonna say I’ve been out of the bar scene for several years now and as each year goes by, I can tolerate a f**kin’ drunk less and less! 
lightweight
I have a rather large tolerance and have frequently taken a sabbatical from the bottle in an effort to reduce the tolerance. I have found that my tolerance for the most part remains the same but I feel it more the next day.
Age and metabolism also figure into your alcohol tolerance. To continue on the anecdote train, I found that my tolerance virtually disappeared once I turned the corner of 30 years old (or thereabouts) and I know a few folks who report the same thing.
The thing I’m trying to figure out is that it wasn’t a complete loss of tolerance… physically I can still handle large amounts of alcohol quite well, walking, talking, making omlettes, etc… but my judgement takes a huge nosedive and the hangovers are worse than ever before. They’ve gone from a morning cottonmouth to day-long existential/depressive crises. (Needless to say, I’m quite careful about my drinking these days).
Alcohol tolerance is a funny thing. From a simpleminded physiological perspective, you’d expect it to take about 5 days to induce liver alcohol dehydrogenase, and maybe a week or two to de-induce the enzyme. The reality is a good deal more complicated:
With tolerance having been shown to be affected by environmental cues:
it’s going to be tough to come up with a hard and fast number as to how long it lasts. Are you asking about tolerance in the bar, or at your second cousin, twice removed’s wedding reception? The answer will be different.
for me, about a month
ive investigated this very literally. i used to drink a hell of a lot as a student, very high tolerance, very expensive habit. after uni i totally quit and didnt touch a drop for 3 years. i have now returned to having the occasional drink in social situations but i did have one big drinking session shortly after starting again.
i found i got merry after the very first drink, however my capacity turned out to be not much less than it used to be, just the process of getting drunk took hold faster.