So they were trying to dig up the time capsule in S13E9 and R brought out pictures she took so it could be found. K makes the pictures about himself, of course, claiming he now has a six pack. But its funny how it turns into making fun of him.
If I was just watching this scene in real time, I would assume that the six pack abs thing is a running joke in the family. But now that he's claimed that Janelle only wants him for his ripped body, it seems to unfortunately be serious
It's also interesting that he and Christine seem to be the slimmest at this point. Seriously, when he was claiming to not be attracted to her and cutting her off sexually, she was even skinnier.