Kylie Jenner tried to be funny the other day and wore a graphic t-shirt (no that's not the joke, but yeah it's still pretty shocking to see a Kardashian-Jenner wear anything that costs less than Kim's soul) that said “I'm Somebody's DUFF”. If you don't know what a DUFF is, then you probs are one. It stands for “Designated Ugly Fat Friend” aka the girl in the friend group that makes the other girls look better aka book version Jenny Humphrey.
It's nice that Kylie is being ironic, maybe she's finally passed the 10th grade, but it's really just a backdoor compliment. Maybe she's “Ugly and Fat” in the “my pores are massive before my morning facial, and I broke 110 pounds last week” kind of way, but compared to the rest of the American population (see anyone at Six Flags) she's doing just fine.