Table 4.
Summary of intervention studies comparing packaged versus unpackaged energy-dense, nutrient-poor snack containing same total serving size.
| First Author, Year of Publication, Country, Risk of Bias | Study Sample | Setting | Package Size Comparison Groups | Potential Moderators or Mediators | Outcome Measures (Measures Used) | Findings |
|---|---|---|---|---|---|---|
| Argo, 2012 Study 1 [48] Canada Low |
76 female undergraduate students | Laboratory face-to-face | Gumdrops 85 g loosely in a bowl Five 17 g small packs in a bowl |
Appearance self-esteem (ASE) | Consumption (direct weighing) | Participants consumed significantly more when snacks were in small packages compared to when snacks were loose, which was fully contributed by those with low ASE (22 g/129% more from packaged than loose snacks). No effect of the presence of small package on consumption was found among participants with high ASE. |
| Argo, 2012 Study 4 [48] Canada Low |
297 female undergraduate students | Laboratory face-to-face | Candy-coated chocolates (88 chocolates) A bowl of loose chocolates Eight small packs |
ASE Energy information labelling |
Consumption (direct weighing) | Participants consumed significantly more when snacks were in small packages compared to when snacks were loose, which was fully contributed by those with low ASE (28 g/350% more from packaged than loose snacks). No effect of the presence of small package on consumption was found among participants with high ASE. Participants with low ASE consumed significantly more from packaged snacks when they were informed the energy content of small packages was low (compared with when they were informed the energy content was high or when no energy content information). |
| Argo, 2012 Study 5 [48] Canada Low |
105 female undergraduate students | Laboratory face-to-face | Candy-coated chocolates (88 chocolates) A bowl of loose chocolates Eight small packs |
ASE Cognitive load (memorising numbers) 1 |
Consumption (direct weighing) | Participants with low ASE consumed significant more (17 g/81%) when snacks were packaged than when snacks were loose. Participants in the low cognitive load condition consumed significantly more (14 g/74%) from snacks that were packaged than from snacks that were loose. |
| Chance, 2014 Study 2 [61] The USA High |
Office kitchen of a technology company | Free living | M&M’s Loose M&M’s in a bulk container M&M’s in small fun packs |
None | Consumption (direct observation by trained research assistants) | Participants consumed significantly less (178 kcal/58%) on each occasion when snacks were in smaller packages (fun packs) than when snacks were loosely in the bulk container. |
| Knowles, 2020 Study 1 [62] The UK Low |
80 university students (68 females) Mean age 21 years |
Laboratory face-to-face | Brownies Unwrapped in a transparent bowl Wrapped individually in plastic film in a transparent bowl |
Perceived effort 2 Visual salience 3 |
Consumption (direct weighing) | Participants consumed significantly less when snacks were individually wrapped than when snacks were unwrapped. The perceived effort was a moderator. Unwrapped snacks required less perceived effort to attain than wrapped snacks. The visual salience was a moderator. Unwrapped brownies had a higher visual salience than wrapped brownies. |
| Cheema, 2008 Study 1 [63] The USA High |
22 female undergraduate students | Free living | Chocolates (6 pieces in a box) Unwrapped Wrapped individually in foil |
Self-regulatory concern (aversion to overconsume) | Rate of consumption (self-reported response sheet) | All participants were required to finish provided chocolates in a week. Participants consumed wrapped chocolates significantly more slowly than those that were unwrapped (consumed 45 out of 66 pieces in total if wrapped vs. 60 out of 66 in total if unwrapped, in first two days). This effect was fully contributed by participants who had greater self-regulatory concerns. No significant effect was found in participants with no self-regulatory concern. |
| Cheema, 2008 Study 4 [63] The USA High |
54 university students | Free living | Cookies (20 pieces per condition) Unwrapped Wrapped individually in white wax paper Wrapped individually in different colour |
Package colour | Rate of consumption (direct observation) | Participants consumed cookies that were individually wrapped in coloured packages significantly more slowly than those that were individually wrapped in white packages, or those that were unwrapped. Participants with cookies wrapped in white packages had the same consumption rate as participants with unwrapped cookies. A total of 17 of 20 participants finished cookies that were individually wrapped in coloured packages, all 20 participants finished cookies were individually wrapped in white packages or unwrapped. |
1 Cognitive load: participants were given a memory task (memorising numbers) at the start. Participants in low cognitive load condition were required to memorise a two-digit number, whereas those in high cognitive load condition were required to remember an eight-digit number. 2 Perceived effort: the required effort to attain the provided snack. 3 Visual salience: the subjective perception of attractive properties of the provided snack.