Replacing standard packaging with single-serve packaging may help some overweight people to consume less food, according to a small new study.
Although the research wasn't specifically looking at people who were trying to lose weight, it "indicates that single-serving packages may help overweight individuals," author Hollie A. Raynor said by email.
Raynor, a researcher in the Department of Nutrition at the University of Tennessee in Knoxville, wanted to know if single-serving packaging offers cues about the appropriate amount to eat.
She and a colleague recruited people around the university and 64 ended up seeing the study through to the end. Some were overweight and some were healthy weight, and some were watching their food intake while others were not.
Half the participants received a box of 20 single-serving packs of pretzels, each just under one ounce. The rest received two standard-size bags of pretzels, each ten ounces.
Researchers told everyone to take the pretzel bags home for four days, eating as much or as little as they preferred, then return them. Participants were also asked to fill out a form detailing when and where they ate the pretzels.
The researchers estimated how much each person had eaten by weighing the pretzel bags returned to them on day four.
On average, people in the healthy weight group ate about 135 grams of pretzel, compared to 155 grams for the overweight group.
Of those who got bigger bags of pretzels, the healthy weight group ate an average of 112 grams, compared to 204 grams in the overweight group.
But among those who had the single serving packs, the overweight group actually ate less than the healthy weight group, 107 grams compared to 158 grams.
The results were published in the Journal of the Academy of Nutrition and Dietetics.
It is interesting that fat and thin people seemed to differ in opposite directions in this study, said David A. Booth, a professor of psychology at the University of Birmingham in Edgbaston, U.K.
But it's hard to generalize these results for people who are trying to lose weight, he said in an email.
"Only two extreme conditions were contrasted: one packet was 11 times bigger than the other," he said. "Where does the effect cut in?"
It will be more useful once we have comparisons of packages of more similar sizes, he said. And it may not be that overweight people react more strongly to packaging cues, he added - it could be they are more dissuaded by the extra effort of opening lots of little packages than are healthy weight people.
Laurits Rohden Skov, who studies public health and nutrition at Aalborg University in
Copenhagen, Denmark, recommended taking these results "with a pinch of salt."
The study was quite small and the wide variation in consumed pretzels might have been due to many things, he said.
He was not involved in the study, but he thinks it is an important area of research.
"One of the major determinants of modern obesity is overconsumption of calories, and ecological research has shown a link between increasing portion sizes and increasing prevalence of obesity," Skov said.
"People do not eat a reflective and conscious amount of grams when they eat, they eat units, and one unit of pretzels is for many people one bag of pretzels," he said. "Likewise, people finish what they have on their plate, because the plate is perceived as one unit."
He doesn't think overweight people are more susceptible to packaging cues, but that smaller package sizes can help people with low self-control.
For both groups, those who were watching what they ate consumed slightly less than those who were not dieting, but not enough to make a statistical difference, the study authors report in the Journal of the Academy of Nutrition and Dietetics.
"I believe the valid and sensible conclusion we can draw is that packaging can indeed affect intake in overweight or obese people," France Bellisle, a researcher in the Nutritional Epidemiology Unit at Universite Paris 13 in Bobigny, France, said.
But it is difficult to take much from this study because each group of participants was so small, she said.
Single-serve packets tend to be more expensive than bulk packaging, but there are other ways to try to keep your serving sizes down, Raynor said.
"If someone feels this is a helpful option for them, they can make their own single-serving packages with baggies," she said.