Small packets and eating more - implications for carbon labelling?

This study in the Journal of Consumer Research may be relevant to the whole carbon labelling debate. A New Scientist article (Issue 2663, 02 July 2008, p 14) about the study reported:
There is an old dieters' joke that anything eaten directly from the fridge has no calories. Wrong. But surely anything in a teensy snack pack must help you lose weight, right? Wrong again.

Grocery aisles are full of small "diet packs" of candy, cookies or fried snacks, advertised as a guilt-free way of helping you eat less. But Rik Pieters and colleagues at Tilburg University in the Netherlands suspected that diet packs might in fact make people drop their guard and eat more

They had 140 students watch TV - to rate advertising, they were told - and gave them either two 200-gram bags of potato chips or nine 45-gram packs. To activate "self-regulatory concerns", half of the students were asked about weight issues and weighed in front of a mirror - all supposedly as part of another study.
Among students without weight thoughts, three-quarters opened their small bags and half opened their large bags. Both ate about the same amount.

In volunteers primed with a diet mindset, however, just a quarter of students opened their large bags, eating half as many chips as the 59 per cent of students who cracked open the small packs The researchers think people with small bags felt they didn't need to exercise self-control, because it was a pre-portioned pack. The same effect may occur with other seemingly small temptations, such as low-fat or natural foods.

Why are food companies making smaller packages? "Some may truly want to help consumers - although our results suggest they won't," says Pieters. "Some may want to prevent lawsuits by showing it's not their fault consumers are overweight. Or they may know this happens, and want to look good while selling more of their products, at a higher profit."