A fact is a something proven to be true. A fat fact is when someone says something you can relate to and is just an obviously true. Since it’s so relatable it makes it a FAT FACT. It may also be pronounced as Fat Fax
Billy: Spring Break is going to be Lit!
John: FAT FACTS!
While our lifespan is the number of years we will live, our healthspan is the number of healthy years we will have and our sexspan is is the number of years we will continue to be healthy enough to continue having an active sex life.
A lighthearted reaction upon receiving disappointing news of some sort. Usually something that isn't a particularly a big deal, esp. when it primarily affects someone else - sort of a mild schadenfreude. Sometimes doubled or tripled, and possibly said in a sing-songy voice for added comedic effect to imitate a muted trumpet, which is how the meme originated.