Variety of fruit on a buffetIf you're keen on picking your way through the breakfast buffet or making the most of the salad bar, you could be adding inches to your waistline.

According to the latest research, eating a lot of different foods plays a trick on your unsuspecting brain.

Dubbed the "buffet effect" by scientists, the research revealed that people faced with a large variety of food took, on average, 10 per cent more.

And all this variety tricks the brain into believing the body is eating less than it really is.

Over the course of a year, it could add up to a whopping extra stone and a half in weight.

As part of the study, 150 students at the University of Minnesota were shown a standard portion of identical sweets.

They were then asked to pour the same-sized portion of multi-coloured sweets into a bowl but misjudged the size by around 10 per cent.

A separate test found the group similarly unable to judge the size of different portions of single or multicoloured sweets, consistently underestimating the coloured portion.

Scientists believe that a range of different foods creates a kind of optical illusion, leaving the brain unable to correctly judge the portion size.

Writing in the Journal of Consumer Research, the researchers wrote: "Variety seems to make people unknowingly pour larger servings.

"Given that people typically finish what they serve themselves the findings have potential implications for how much people consumer.

"Identical items naturally consolidate into a single whole, making them seem to occupy a larger area."

They did, however, stress that the healthy eaters among us shouldn't limit themselves to one foodstuff, but to be aware of this unusual trick of the eyes.

So next time you head for the 'all you can eat' restaurant deal, remember your eyes could be bigger than your stomach.