Yes, that's the correlation effect. It's intuitive to believe that the association is evidence of cause and effect, and that one will tend to always be thought of as the cause also intuitively. In this case, it's the status of diet guru and their body fat. It's more intuitive to believe that it's their own dietary advice that made them fat, than to believe they became diet gurus precisely because they were fat. Though both are equally valid conclusions.

We could also call it the salesman effect. When you want to sell anything, especially a body image product, you better look your best. That's why we use young beautiful professional female models to sell beauty products, and lean muscular men to sell bodybuilding products. And so the clip is basically a sales pitch.