Impact of decreasing the proportion of higher energy foods and reducing portion sizes on food purchased in worksite cafeterias:A stepped-wedge randomised controlled trial


Background: Overconsumption of energy from food is a major contributor to the high rates of overweight and obesity in many populations. There is growing evidence that interventions that target the food environment may be effective at reducing energy intake. The current study aimed to estimate the effect of decreasing the proportion of higher energy (kcal) foods, with and without reducing portion size, on energy purchased in worksite cafeterias.  Methods and findings: This stepped-wedge randomised controlled trial (RCT) evaluated 2 interventions: (i) availability: replacing higher energy products with lower energy products; and (ii) size: reducing the portion size of higher energy products. A total of 19 cafeterias were randomised to the order in which they introduced the 2 interventions. Availability was implemented first and maintained. Size was added to the availability intervention. Intervention categories included main meals, sides, cold drinks, snacks, and desserts. The study setting was worksite cafeterias located in distribution centres for a major United Kingdom supermarket and lasted for 25 weeks (May to November 2019). These cafeterias were used by 20,327 employees, mainly (96%) in manual occupations. The primary outcome was total energy (kcal) purchased from intervention categories per day. The secondary outcomes were energy (kcal) purchased from nonintervention categories per day, total energy purchased per day, and revenue. Regression models showed an overall reduction in energy purchased from intervention categories of −4.8% (95% CI −7.0% to −2.7%), p < 0.001 during the availability intervention period and a reduction of −11.5% (95% CI −13.7% to −9.3%), p < 0.001 during the availability plus size intervention period, relative to the baseline. There was a reduction in energy purchased of −6.6% (95% CI −7.9% to −5.4%), p < 0.001 during the availability plus size period, relative to availability alone. Study limitations include using energy purchased as the primary outcome (and not energy consumed) and the availability only of transaction-level sales data per site (and not individual-level data).  Conclusions: Decreasing the proportion of higher energy foods in cafeterias reduced the energy purchased. Decreasing portion sizes reduced this further. These interventions, particularly in combination, may be effective as part of broader strategies to reduce overconsumption of energy from food in out-of-home settings. Trial registration: ISRCTN registry ISRCTN87225572.

Publication DOI:
Divisions: College of Health & Life Sciences > School of Psychology
College of Health & Life Sciences > Aston Institute of Health & Neurodevelopment (AIHN)
Additional Information: Copyright: © 2021 Reynolds et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Funding: This research was funded in whole, or in part, by the Wellcome Trust [ref: 206853/Z/17/Z (TMM, GJH)]. For the purpose of Open Access, the author has applied a CC BY public copyright licence to any Author Accepted Manuscript version arising from this submission. CRUK (Cancer Research UK) [ref: C4770/A29425- Health Evaluation Targeted Research (TMM)] and the Wellcome Trust [ref: 106679/Z/14/Z (RP)] also contributed funds towards this research.
Uncontrolled Keywords: Food,Obesity,Employment,Randomized controlled trials,Socioeconomic aspects of health,Overweight,Schools,Social systems,Medicine(all)
Publication ISSN: 1549-1676
Last Modified: 14 May 2024 07:28
Date Deposited: 15 Sep 2021 11:00
Full Text Link:
Related URLs: https://journal ... al.pmed.1003743 (Publisher URL)
http://www.scop ... tnerID=8YFLogxK (Scopus URL)
PURE Output Type: Article
Published Date: 2021-09-14
Accepted Date: 2021-07-27
Submitted Date: 2020-12-21
Authors: Reynolds, James P. (ORCID Profile 0000-0003-1536-1557)
Ventsel, Minna
Kosīte, Daina
Rigby Dames, Brier
Brocklebank, Laura
Masterton, Sarah
Pechey, Emily
Pilling, Mark
Pechey, Rachel
Hollands, Gareth J.
Marteau, Theresa M.



Version: Published Version

License: Creative Commons Attribution

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