What does Lizzo have to be sad about exactly? She has money, connections and way more freedom than any of her sycophant fans. If it's because no man wants her due to her weight, tough shit. Her peers CardiB, Megan and Doja all slimmed down once they made it big because they know that a healthy body is what sells.
In her specific genre of music, you better have a sexy body or you better be funny as shit to keep a people talking about you and Lizzo is no Missy Elliot so she better get to losing some weight. All these articles about her showing her gargantuan ass in ill fitting clothing, and generally being trashy in public is a PR nightmare and no amount of "I'm sad because people make fun of my weight" can save that.