The story that was too good to be true – how journalists fell for 'dark chocolate is good for you' tale

When researchers at Germany's Institute of Diet and Health revealed that eating dark chocolate can help you lose weight, newspapers lapped it up.

The Mail Online's excitable headline was typical of the coverage it generated: "Pass the Easter Egg! New study reveals that eating chocolate doesn't affect your Body Mass Index ... and can even help you LOSE weight!"

The only slight problem with this fantastic tale was that it was exactly that – a tale. The Institute of Diet and Health and its leading authority Johannes Bohannon were nothing more than the work of a prankster's imagination.

Bohannon was in fact the alter ego of John Bohannon, a science journalist. It was true that Bohannon was conducting an experiment – but what the journalists didn't pick up on was that he was testing their gullibility.

Bohannon came clean this week, authoring a piece for the io9 site headlined: "I fooled millions into thinking chocolate helps weight loss. Here's how."

He wrote: "I am Johannes Bohannon, Ph.D. Well, actually my name is John, and I’m a journalist. I do have a Ph.D., but it’s in the molecular biology of bacteria, not humans. The Institute of Diet and Health? That’s nothing more than a website."

Bohannon explained that as part of a team of gonzo journalists and one doctor, they did run a real clinical trial "...and the statistically significant benefits of chocolate that we reported are based on the actual data".

As he writes: "It was, in fact, a fairly typical study for the field of diet research. Which is to say: It was terrible science. The results are meaningless, and the health claims that the media blasted out to millions of people around the world are utterly unfounded."

When the results were published in unquestioning science journalists, that was enough to convince time-poor reporters that the story had some merit.

Bohannon said the aim was to demonstrate " just how easy it is to turn bad science into the big headlines behind diet fads".