Even a cyber-nurse giving advice anonymously online may have more credibility than a real-life fat one, the study said.
University of Chichester psychologists quizzed 98 people aged 18 to 85.
They were asked to rate advice given by an imaginary nurse “with ten years’ experience” and shown a silhouette of her as a healthy weight or clearly obese.
They were then shown another image where she had either lost or gained weight and asked to rate her advice again.
Ratings rose in those who saw her weight loss and fell in those who saw her become obese.