Yo Mama's so fat that she was instructed by the doctor to go on a low carbohydrate, high protein diet to reduce the risk of heart disease or even a heart attack later in life.
Anti-humor is a type of indirect humor that involves the joke-teller delivering something which is deliberately not funny, or lacking in intrinsic meaning. The practice relies on the expectation on the part of the audience of something humorous, and when this does not happen, the irony itself is of comedic value.