For people to associate their food, not with unhealthy lifestyles but au contraire with lifestyles that Evoque nutrition-consciousness.
As we now, classical conditioning happens thanks to an association. In the olden days, doctors used to advertise cigarettes, for people to see cigarettes as a healthy habit. By associating doctors and cigarettes people will assume that smoking wasn't that bad because a Doctor who is a person concerned with health was recomending them.
The same principle applies here.
Seeing an athlete recommending a certain brand of fast food would make people think that maybe, that particular brand is healthier than others.
