Scientists at the University of Colorado Denver found that study participants consumed nearly 187 fewer grammes of snacks per week when given 100kcal snack packs compared to standard size packages of snacks.
Published online this week in Elsevier's Appetite review, researchers also found that initial exposure to portion-controlled packages may well have increased awareness of portion size for the 59 study participants, resulting "in reduced overall consumption, even when larger packages were available", say the scientists.
Reducing portion sizes, say food industry observers encouraging snack makers to downsize their products, could be part of the solution to arrest galloping obesity rates in Europe.
The UK government estimates that a potential nine out of 10 children could be overweight or obese by 2050.
The country's Food Standards Agency is currently exploring how changes in portion sizes of everyday foods have affected people's energy intake, weight gain and diet,
"Portion sizes our part of our wider saturated fats and energy intake campaign, and we're encouraging food manufacturers to make foods available in smaller portions," a spokesperson for the agency said to BakeryandSnacks.com.
And last month the UK's health secretary Alan Johnson challenged the industry to design healthy snacks in smaller portions.
The health secretary called on the industry "to cut portion sizes and promote healthy snacks to help consumers to lose weight," a press officer at the Department of Health told BakeryandSnacks.com.
And this latest small study from the US is set to fuel the debate.
In a cross-over study, 59 participants were randomly assigned to receive either 100 kcal packs or standard size packages of snacks for one week. After a minimum of a one week washout period, participants received the other form of the snack for a further week.
Snack consumption was recorded by participants in a diary. According to the results, participants consumed an average of 186.9 fewer grams of snacks per week when receiving 100 kcal snack packs compared to standard size packages of snacks.
Post-hoc comparisons revealed the effect of package size depended on both randomisation order and study week, say the scientists from the Center for Human Nutrition at the University of Colorado Denver.
Total grammes of snacks consumed in week one "differed significantly" between the two randomised groups. In week two, however, grammes of snacks did not differ significantly between the two groups.
"This interaction was primarily due to a significantly lower consumption of snacks from standard size packages in the week following the portion-controlled packages," write the researchers, suggesting that the initial exposure to portion-controlled packages might have increased awareness of portion size, "such that less was consumed when larger packages were available."
Nutrition labels vs portion size
Feeding the debate in a different vein, sister site NutraIngredients.com reported in January this year on a US-Norwegian study that suggested nutritional labelling may mean more to consumers than portion sizes.
According to findings published in the Journal of the American Dietetic Association, “information about portion size was not found to be a good tool to manipulate food-intake behaviour in this study," wrote lead author Oydis Ueland from Nofima Food in Norway.
Source: Appetite Published online ahead of print 9 March 2009“Do calorie-controlled portion sizes of snacks reduce energy intake?” Authors: N. Stroebele, L.G. Ogden, J.O. Hill