Lose weight by changing the colour of your plate Those given crockery which "matched" their food - red for tomato sauce, or white for cream sauce - gave themselves helpings between 17 and 22 per cent larger than those with plates of contrasting colour. 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 by researchers at Cornell University, in New York state, 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. Research authors said the colour contrast appears to act as a "stop sign" reminding people to think about how much food they were serving. Prof Brian Wansink, who runs Cornell University's Food and Brand Lab, which studies consumer behaviour, said: "People will generally serve themselves far more on a large dinner plate than they would on a smaller one, because the eye is tricked. It seems that colour contrast is one way to block this illusion. The research author said those trying to lose weight could help themselves by buying brightly coloured or dark 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. Prof Wansink, president of the US Society for Nutrition Education and Behaviour 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. Previous research by Prof Wansink has found that people eat 22 per cent less when they replace 12 inch dinner plates - now the average size used in the UK - with 10 inch plates, which were the most commonly used a decade ago. Regardless of the size of their plate, people tend to fill around 70 to 80 per cent of it, he said, and to eat almost all of any portion they served themselves. The lab's studies have also found that people pour far less into short wide glass than they do tall ones, and that children prefer meals with lots of different colours in them.