Many people find it hard to restrict themselves to just one packet when eating snack-sized portions, and are also more likely to tuck into the treats than if they had a big bag, concluded researchers from Tilburg University, Netherlands.
This may also result in higher consumer spending.
This brings into question the effects that individually wrapped single-portion schemes, initiated by companies such as Kraft, Ben & Jerry's, Pringles and Lays, can have on eating habits and rising obesity levels.
"These industry developments are consistent with the assumption that when products… are offered in small packages formats, consumers are better able to restrain the total quantity consumed," wrote the authors of the report, which was published in the Journal of Consumer Research.
"We speculate that the actual purchase of multipacks of single-serve formats may itself satisfy consumers' needs to self-regulate, causing them to let their guard down."
The studies In the first study, 59 undergraduate students were asked about what motivates them for buying different sized packages.
Smaller packages where perceived to help self-regulate consumption, while it was considered more difficult to restrict intake with larger packages.
However, study two showed quite the opposite happened in reality.
One hundred and forty undergraduate students (59 females and 81 males) were asked to watch television, under the false impression they had to rate advertising.
They were given either nine small 45g bags of crisps or the same amount of crisps in two large 200g bags, to eat while watching television.
Half were primed to think about calories, by being asked if they had any concerns about their size and weighed in front of a mirror.
Overall, 52.1 per cent of the participants (73 out of 140) opened a bag of crisps while watching the television, with the average consumption being 49.8 grams for those who took the plunge.
Bag size was not shown to have any effect on the amount of crisps eaten by those not made to think about weight.
"However, when self-regulatory concerns were activated, consumers were almost twice as likely to start consuming tempting products from small as compared to large package formats and - if they did - consumed nearly twice as much," wrote the authors.
Consumption proved to be at the lowest level when self-regulatory concerns were activated by previous questions on weight.
The scientists said: "Small package formats may fly under the radar and prevent such internal control, thereby leading to consumption misregulation.
Because they are also willing to pay a price premium for tempting products in small package formats, in particular, consumers with self-regulatory concerns might wind up consuming more rather than less at a higher price."
The scientists said the potential long-term costs of eating products in smaller packages again and again would be a valid area for follow-up research.
Source: Journal of Consumer Research October 2008, published online ahead of print, DOI:
10.1086/589564 "Flying under the Radar:
Perverse Package Size Effects on Consumption Self-Regulation" Authors: Rita Coelho Do Vale, Rik Pieters, Marcel Zeelenberg