Child and adult snack food intake in response to manipulated pre-packaged snack item quantity/variety and snack box size: a population-based randomized trial



Snacks contribute to overconsumption of energy-dense foods and thence obesity. Previous studies in this area are limited by self-reported data and small samples. In a large population-based cohort of parent–child dyads, we investigated how modification of pre-packaged snack food, i.e. (a) item quantity and variety, and (b) dishware (boxed container) size affected intake.


Design: Randomized trial nested within the cross-sectional Child Health CheckPoint of the Longitudinal Study of Australian Children, clustered by day of visit. Sample: 1299 11–12 year olds, 1274 parents. Exposure: 2 × 2 manipulation of snack box container size and item quantity/variety: (1) small box, few items, (2) large box, few items, (3) small box, more items, (4) large box, more items. Procedure: Participants received a snack box during a 15 min break within their 3.5 h visit; any snacks remaining were weighed. Outcomes: Consumed quantity (grams) and energy intake (kilojoules). Analyses: Unadjusted linear regression.


Children who were offered a greater quantity and variety of snack items consumed considerably more energy and a slightly higher food mass (main effect for energy intake: 349 kJ, 95% CI 282–416, standardized mean difference (effect size) 0.66; main effect for mass: 10 g, 95% CI 3–17, effect size 0.17). In contrast, manipulating box size had little effect on child consumption, and neither box size nor quantity/variety of items consistently affected adults’ consumption.


In children, reducing the number and variety of snack food items available may be a more fruitful intervention than focusing on container or dishware size. Effects observed among adults were small, although we could not exclude social desirability bias in adults aware of observation.

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The authors thank all families, senior researchers, research assistants, students, and interns who assisted in CheckPoint data collection and management. They also acknowledge all families for their continued participation in Growing Up in Australia, the Longitudinal Study of Australian Children (LSAC). LSAC is conducted in partnership between the Department of Social Services (DSS), the Australian Institute of Family Studies (AIFS), and the Australian Bureau of Statistics (ABS). The findings and views reported in this paper are those of the authors and should not be attributed to DSS, AIFS, or the ABS. REDCap (Research Electronic Data Capture) electronic data capture tools were used in this study. More information about this software can be found at We thank the LSAC and CheckPoint study participants, staff, and students for their contributions.


The Child Health CheckPoint has been supported to date by the Australian National Health and Medical Research Council (NHMRC) (1041352, 1109355), The Royal Children’s Hospital Foundation (2014-241), Murdoch Children’s Research Institute, The University of Melbourne, National Heart Foundation of Australia (100660), Financial Markets Foundation for Children (2014-055), and Victorian Deaf Education Institute. The following authors were supported by the NHMRC: MW, Senior Research Fellowship 1046518; FKM, Early Career Fellowship 1037449, Career Development Fellowship 1111160; LG, Early Career Fellowship 1035100. PWJ was supported by the Dutch Diabetes Foundation (2013.81.1664), and MW additionally by Cure Kids New Zealand. Research at the Murdoch Children’s Research Institute is supported by the Victorian Government’s Operational Infrastructure Support Program.

Author information

MW conceived the trial. The trial was designed by JAK, PWJ, FKM, and MW, with guidance by senior hospital dietitian KG. JAK conducted the statistical analysis, in consultation with FKM and JBC. JAK wrote the first draft of this manuscript, which was revised by PWJ, FKM, KG, TSO, JBC, SAC, DB, LG, LAB, and MW. All authors have seen and approved the final version.

Correspondence to Jessica A. Kerr.

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The authors declare that they have no conflict of interest.

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Trial registration: ISRCTN12538380.

Supplementary information

Supplementary Table 1: Gram intake by participant characteristics and experimental condition

Supplementary Table 2: Kilojoule intake by participant characteristic and experimental condition

Supplementary Table 3: Sensitivity analysis for child and adult gram consumption

Supplementary Table 4: Sensitivity analysis for child and adult kilojoule consumption

Supplementary Figure titles

Participant retention LSAC B-Cohort through to CheckPoint

Supplementary Figure 2: Grams consumed and unconsumed per item, clockwise from Peaches

Supplementary Figure 3: Kilojoules consumed and unconsumed per item, clockwise from Peaches

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