I don't recall Maybelle's weight being a plot point, as it is with Tracey and her mom.
Wilmingtom, Maybelle's weight is certainly a plot point in the show. The fact that she is larger and unashamed, while being a public figure on television, helps give Edna the assurance she needs to break out of her shell, fight for equality, and "appear on TV at [her] present weight." This is followed by Maybelle's line: "You can't let weight restrict your fate. Look at me; I'm on TV." Then, she sings "Big, Blonde, and Beautiful," a song filled with lyrics about being overweight.