Page last updated at 17:04 GMT, Wednesday, 2 July 2008 18:04 UK

How 'snack-size' makes you bigger

Boy eating chocolate
Bite size snacks can be very moreish

Buying mini-versions of fattening snacks is not the way to keep weight off, Dutch scientists claim.

Few people have enough willpower to restrict themselves to just one, they say, and can end up eating more than intended.

New Scientist magazine reports how weight-conscious students were asked to choose between a big bag of crisps and several, smaller ones.

Most opened the little ones - but ended up eating twice as many crisps.

You are just more conscious of what you are eating if you have a proper-sized snack
Nadine Field

Dr Rik Pieters and his colleagues from Tilburg University suspected that "snack-size" treats actually might make people more complacent about eating more.

His student volunteers were asked to watch television - telling them to rate the quality of the adverts they were shown.

Unknown to them, the real focus of the research was the crisps they were given at the same time.

The students had earlier been split into two groups - one of which was "primed" to think about weight by being weighed in front of a mirror and asked about weight issues, supposedly as part of another study.

There were two sizes of snack on offer in the television room - one 200 gram bag of crisps, and nine smaller 45 gram bags.


Three-quarters of the students who had not been primed about weight chose to open the smaller bags, and half opened the bigger bag.

All the students ate roughly the same amount.

However, in the "weight conscious" group, only a quarter of the students opened the large bags, and 59% opened the smaller bags.

But those who opened the smaller bags ended up eating twice as much.

Dr Pieters, whose findings were originally published in the Journal of Consumer Research, suggested that people who opened smaller bags may have felt they did not need to exercise as much self control, because the portion size was fixed.

Psychologist Nadine Field said that the research would ring true to many people who had munched their way through several small packets of sweets or chocolates in one sitting.

"You are just more conscious of what you are eating if you have a proper-sized snack. Having a smaller size is a comforting delusion really.

"Most of us have done this at one time or another."

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