Can’t take alcohol like I used too

I’m a 23m and even just a couple years ago I could drink 10-12 beers in a night and not feel horrible. In this past year 4 beers is my absolute limit, anything after that I just start feeling like shit, and the next day is even worse. I don’t mind because I get a buzz and it’s significantly decreased my alcohol consumption. Just wondering if anyone else has had their capabilities with alcohol diminished really quickly like that? I see people who are older than me who can chug beers like it’s nothing and it amazes me. Do they feel like shit and just do it anyway or does their body just work differently?