"You look like your mother, FATTIE!" ^^^^^^^^^^^^^^^^^^^^Context is above ^^^^^^^^^^^^^^^^^^^^
Obese specifically refers to the fact that Your Mother has packed on a seemingly absurd amount of fat.
Anyone ever seen an obese hippy at festival?
Nope.
Neither.
My very fat fish
Friend: “What’s your fishes name?”
Me: “I don’t know, maybe Fatty Patty? Or Obese Denise?”
Friend: “How about Obese Fatty Denise Patty?”
Me: “GrEaT iDeA”