For those keen to lose weight, cutting out chocolate would seem to be common sense.

But banishing all thoughts of chocolate could actually end up making you fatter.

Psychologists have discovered that those who try to stop thinking about chocolate eat nearly 50 per cent more than those who have a more liberal approach to their craving.

They say it could explain why some women are prone to "yo-yo" dieting or go on to develop binge-eating disorders.

Psychologist James Erskine, of the University of Hertfordshire, who led the independent research, said: "The act of avoidance seems to completely backfire.

"We found that if you try not to think about eating chocolate, it tends to lead you to eat more. In other words, thinking about chocolate is not dangerous – but trying not to think about it is."

Dr Erskine, who calls the phenomenon a "behavioural rebound", claims his findings could help those struggling to give up unhealthy foods and even smoking.

The study, called "Resistance Can Be Futile", and published in the scientific journal Appetite, looked at 134 undergraduates.