They recruited female volunteers who signed up for a weight-loss program and gave them diaries in which the volunteers could note down precisely what they ate and when — a standard technique in weight-loss programs nowadays.

But half the volunteers got a diary that featured a skinny model on the cover and on every page. The other half got diaries with the neutral image of a logo.

The results were sobering.

“Those people that saw the diary without the model on top — they were actually able to lose weight,” Klesse said. “Surprisingly, the people that [had the diary with the model on it] were not able to lose weight, and even worse, they even slightly gained weight.”