I don't know if this counts as fat joy but I think it does. I've always been very insecure specifically about the shape of my body and how I gain weight. My mum was fat but "pear shaped", for lack of a better word, and said a lot of mean things about me and my dad (who I take after, shape wise), because when we gain weight it all goes to our belly. We're "chicken limbs and a pot belly" shaped. Before I transitioned, she told me I had to keep a better eye on weight because "if you get fat you'll look pregnant and you don't want that". She (thankfully, honestly) died before she saw me transition, and I feel bad saying she was fatphobic, because she was fat herself, but she always tried to teach me that there was a right way to gain weight and that I specifically had to stay thin.
I'm starting my gaining journey but it's been slow. Her comments really got to me and I had an ED for awhile partly because of the way she treated me. I'm obsessed with a (now deceased) celebrity I won't name for privacy reasons, but he gained weight at one point for a film role and then didn't lose this weight after. He looked sooooo good. And there's one video of him, towards the end of his career, in a pretty figure hugging shirt. And that figure? Is just like mine! Skinny limbs, no hips, no ass, big big belly and round double chin. He's bigger than me in that video but it gives me hope. There's no "right" shape to be fat, and when I do get as big as he did (and bigger!) I'll be just as sexy.