Researchers from the Cornell University in New York found that people take far more generous helpings when the food they eat is the same colour as the crockery on which it is placed.
When the food "blends in" with their background, people serve themselves 20 per cent more than if they were serving the same meal on a plate of contrasting colour, they found.
"It seems that colour contrast is one way to block this illusion," said study researcher Brian Wansink, a professor who runs Cornell University's Food and Brand Lab.
Those trying to lose weight, Prof Wansink said, can help themselves by using bright or dark coloured plates to provide contrast with common white foodstuffs such as pasta, rice and potatoes. Alternatively, green plates could be used as a way to trick children into eating more vegetables, he said.
"The secret of weight loss is a couple of small changes. One small difference like this every day could add up to a lot of pounds over a year," Prof Wansink was quoted as saying by the Sunday Telegraph.
In the study, party goers were given either a red or a white dinner plate and led to one of two buffet tables offering pasta; one in tomato sauce, the other in cream sauce.
It was found that those given crockery which "matched" their food gave themselves helpings between 17 and 22 per cent larger than those with plates of contrasting colour.
The researchers believe the phenomenon occurred because many people unthinkingly fill their plate whatever size it is. A high contrast between colours may act as a "wake-up call" to examine the actual size of the portion.
Previous studies have already shown that buffet diners take bigger portions when given bigger plates, aided by an optical illusion which means a circle -- or portion of food -- appears bigger on a small plate than it does on a large one.
Further research has established that the average person eats around 92 per cent of a portion they serve themselves.
The latest study, which was repeated several times on groups of 60 participants, found the actual colour of the food and plates made no difference; what mattered was the contrast between the two.