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

James P. Reynolds*, Minna Ventsel, Daina Kosīte, Brier Rigby Dames, Laura Brocklebank, Sarah Masterton, Emily Pechey, Mark Pilling, Rachel Pechey, Gareth J. Hollands, Theresa M. Marteau*, Barry M. Popkin (Editor)

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

Abstract

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.
Original languageEnglish
Article numbere1003743
JournalPLoS Medicine
Volume18
Issue number9
DOIs
Publication statusPublished - 14 Sep 2021

Bibliographical note

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.

Keywords

  • Food
  • Obesity
  • Employment
  • Randomized controlled trials
  • Socioeconomic aspects of health
  • Overweight
  • Schools
  • Social systems

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