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Increasing the proportion of healthier foods available with and without reducing portion sizes and energy purchased in worksite cafeterias: protocol for a stepped-wedge randomised controlled trial.

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Kosīte, Daina 
Rigby Dames, Brier 
Brocklebank, Laura A 
Pilling, Mark 


BACKGROUND:Overconsumption of energy from food contributes to high rates of overweight and obesity in many populations. A promising set of interventions tested in pilot studies in worksite cafeterias, suggests energy intake may be reduced by increasing the proportion of healthier - i.e. lower energy - food options available, and decreasing portion sizes. The current study aims to assess the impact on energy purchased of i. increasing the proportion of lower energy options available; ii. combining this with reducing portion sizes, in a full trial. METHODS:A stepped-wedge randomised controlled trial in 19 worksite cafeterias, where the proportion of lower energy options available in targeted food categories (including main meals, snacks, and cold drinks) will be increased; and combined with reduced portion sizes. The primary outcome is total energy (kcal) purchased from targeted food categories using a pooled estimate across all sites. Follow-up analyses will test whether the impact on energy purchased varies according to the extent of intervention implementation. DISCUSSION:This study will provide the most reliable estimate to date of the effect sizes of two promising interventions for reducing energy purchased in worksite cafeterias. TRIAL REGISTRATION:The study was prospectively registered on ISRCTN (date: 24.05.19; TRN: ISRCTN87225572; doi:



Obesity, Availability, Randomised Controlled Trial, Choice Architecture, Portion Size, Workplace Interventions, Stepped Wedge Trial, Healthier Eating, Physical Micro-environment Interventions, Nudging

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Cancer Research UK (C4770/A29425)
Wellcome Trust (206853/Z/17/Z, 106679/Z/14/Z)