It could be fat shaming or it could be people who are frequently fat shamed through their life by being called lazy assume anyone who is telling them they aren't putting in enough effort are also fat shaming since the accusation is that they inferred that is what it meant.
Bullshit, Lizzo promotes this type of cancerous behavior. By her own standards, she fat shamed others. There's no other context needed. She's a hypocrite who bullied others. Stop defending her. It's comical how morons like you bitch and moan about believing victims when it's some right wing guy doing it but the moment the abuser is on "your side", you're all of a sudden pro context, impartiality, and evidence.