The Daily Mail
Shelling nuts or unwrapping sweets can cut calories by 40 percent
Snackers could cut down on their calories by up to a staggering 40 per cent just by buying treats in wrappers or nuts still in their shells, according to a new study.
U.S. academics found that when people were given pistachios to eat, the sight of the empty shells acted as a visual reminder of how much they had eaten.
Named the Pistachio Effect, it was found the pile of shells discouraged snackers from eating too many more.
Although the study was carried out using pistachios, the same effect could also apply to piles of sweet wrappers on a desk, which could make the eater feel guiltier about how many they have consumed.
The experiment was carried out by researchers from the Eastern Illinois University, who handed out pistachios to 140 students as they went into lessons.
Half were given the snacking nuts still in their shells and half given the same amount but still in their shells.
At the end of class, researchers discovered that those eating the shelled version consumed an average of 211 calories each.
But those who needed to open the shells and take out the nuts, leaving the shells on their desks, consumed an average 125 calories each, a reduction of 41 per cent.
Some of this is probably down to the sheer inconvenience of having to shell the food, but the researchers believe the major factor is being able to see, by empty shells, just how much they have eaten.
The research was published in the online medical journal Appetite which said the study related to the previously researched Pistachio Effect.
This is where visual clues to what's been eaten can reduce consumption such as eating sweets and leaving the wrappers lying around.
The guilt at being reminded of just how much is being scoffed can jolt the consumer into eating less, it is believed.
Pistachios are a popular snack with those trying to find a healthier alternative to chocolate, sweets or crisps. But while they are healthier, it could be easy to eat too many.
Leaving the shells provides a 'visual cue' said the study by James Painter, of the School of Family and Consumer Sciences at Eastern Illinois University.
He said: 'In-shell nuts help slow consumption and the empty shells offer a visual cue, reducing calorie intake.
'The term 'Pistachio Principle' has been coined to describe a simple technique that can be used to help fool yourself full.' In some of the tests, the empty shells were removed at two hour intervals.
Painter said: 'When leftover pistachio shells remained on the desk throughout the day, calorie consumption of pistachios decreased by 22-percent compared to when nut shells were routinely removed.
'Choosing in-shell pistachios instead of shelled nuts is a simple way to decrease calorie consumption without restriction.
'This is in keeping with existing research showing that when a person has visual cues of 'leftovers,' they can see how many or how much they have eaten, helping to control portion size and consumption.'