I'm not sure which lesson you're talking about but any time I have heard of a "muffin top" it's the fat that sits on your jeans. It's when the person's jeans are too tight and everything else "spills" over. Think about the bakery treat, the muffin. Can you picture it? Little bottom body with a big top that just flows over. I would assume this muffin top is something else but you mentioned the butt lesson so I think I may be thinking of the same thing.