It may be bad manners, but eating noisily could be good for your waistline. Research has shown that we eat less when we can hear ourselves chew.

Ryan Elder, of Brigham Young University in Utah in the US, said: "Sound is typically the forgotten food sense. But if people were more focused on the sound food makes, it could reduce consumption."

Dr Elder made the finding after asking several groups of volunteers to do taste tests and measuring how much food they ate.

In one, 71 students were asked to rate the taste of a type of pretzel while wearing headphones. Half heard loud noise, which drowned out the sound of their chewing, and they got through four pretzels each. The others were able to hear themselves eat and only consumed 2.8 pretzels, on average.

Dr Elder explained: "The effect may not seem huge - one less pretzel - but over the course of a week, month, or year, it could really add up."


In another experiment, 156 students were asked to rate biscuits made of pitta bread.
Before they ate them, half of the volunteers read packaging which described the crackers as "crispy" while the others were simply told they were "tasty" and "delicious". Both groups were then given the same biscuits to eat - but those who had been made to think of them as being crunchy ate fewer.

Writing in the journal Food Quality and Preference, Dr Elder said he isn't sure why eating noisily has such a noticeable effect.

It may be that the act reminds us of how much we are eating. It is also possible we tire of eating more quickly when it is a louder experience.

Whatever the reason, it could help to explain why we tend to munch mindlessly in front of the TV or at the cinema - and means that people could lose more weight simply by eating in silence.

Dr Elder said: "When you mask the sound of consumption, like when you watch TV while eating, it may cause you to eat more than you would normally."

But while the crunch factor could lead to us eating less, we may enjoy the food more.
Previous British research has shown how crisp foods trigger the brain's pleasure centres, with the sound of biting into an apple the most enjoyable.

The makers of Magnum ice cream learned this lesson the hard way.

In response to criticism that the chocolate coating was too brittle, they produced a softer one - only to be told by customers they missed the cracking sound of the original. A return to the first formulation soon followed.