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Protocol of a natural experiment to evaluate a supermarket intervention to improve food purchasing and dietary behaviours of women (WRAPPED study) in England: a prospective matched controlled cluster design
  1. Christina Vogel1,2,
  2. Sarah Crozier1,
  3. Preeti Dhuria1,
  4. Calum Shand1,
  5. Wendy Lawrence1,2,
  6. Janet Cade3,
  7. Graham Moon4,
  8. Joanne Lord5,
  9. Kylie Ball6,
  10. Cyrus Cooper1,2,
  11. Janis Baird1,2
  1. 1 Medical Research Council Lifecourse Epidemiology Unit, University of Southampton, Southampton, UK
  2. 2 National Institute for Health Research Southampton Biomedical Research Centre, University of Southampton and University Hospital Southampton NHS Foundation Trust, Southampton, UK
  3. 3 School of Food Science and Nutrition, University of Leeds, Leeds, UK
  4. 4 Geography and Environmental Science, University of Southampton, Southampton, UK
  5. 5 Southampton Health Technology Assessments Centre, University of Southampton, Southampton, UK
  6. 6 Institute for Physical Activity and Nutrition Research, Deakin University, Burwood, Victoria, Australia
  1. Correspondence to Dr Christina Vogel; cv{at}


Introduction Poor diet is a leading risk factor for non-communicable diseases and costs the National Health Service £5.8 billion annually. Product placement strategies used extensively in food outlets, like supermarkets, can influence customers’ preferences. Policy-makers, including the UK Government, are considering legislation to ensure placement strategies promote healthier food purchasing and dietary habits. High-quality scientific evidence is needed to inform future policy action. This study will assess whether healthier placement strategies in supermarkets improve household purchasing patterns and the diets of more than one household member.

Methods and analyses This natural experiment, with a prospective matched controlled cluster design, is set in discount supermarkets across England. The primary objective is to investigate whether enhanced placement of fresh fruit and vegetables improves household-level purchasing of these products after 6 months. Secondary objectives will examine: (1) differences in intervention effects on purchasing by level of educational attainment, (2) intervention effects on the dietary quality of women and their young children, (3) intervention effects on store-level sales of fruit and vegetables and (4) cost-effectiveness of the intervention from individual, retailer and societal perspectives. Up to 810 intervention and 810 control participants will be recruited from 18 intervention and 18 matched control stores. Eligible participants will be women aged 18–45 years, who hold a loyalty card and shop in a study store. Each control store will be matched to an intervention store on: (1) sales profile, (2) neighbourhood deprivation and (3) customer profile. A detailed process evaluation will assess intervention implementation, mechanisms of impact and, social and environmental contexts.

Ethics and dissemination Ethical approval was obtained from the University of Southampton, Faculty of Medicine Ethics Committee (ID 20986.A5). Primary, secondary and process evaluation results will be submitted for publication in peer-reviewed scientific journals and shared with policy-makers.

Trial registration number NCT03573973; Pre-results.

  • nutrition & dietetics
  • public health
  • preventive medicine
  • health economics

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  • Contributors CV and JB conceived the study, designed the intervention and evaluation, and wrote the first draft of the study protocol and manuscript. SC, CC, KB, JL and GM contributed to the study design and SC, JC, WL, PD and CS aided development of the measures. SC conducted sample size calculations and designed the statistical analyses with input from CV and JB; JL designed the economic evaluation and CV, WL and PD designed the qualitative methods. All authors contributed to revising the manuscript and all read and approved the final manuscript.

  • Funding This research and the authors of this paper are supported by the following funding sources: National Institute for Health Research (NIHR) Public Health Research Programme (17/44/46), NIHR Southampton Biomedical Research Centre, UK Medical Research Centre and University of Southampton. KB is supported by a Principal Research Fellowship from the Australian National Health and Medical Research Council (NHMRC).

  • Disclaimer The views expressed in this publication are those of the author(s) and not necessarily those of the NHS, the NIHR, the UK Department of Health and Social Care or NHMRC.

  • Competing interests This study involves a non-financial collaboration with Iceland Foods. CV, SC, PD, CS, JC, GM, JL and KB have no conflicts of interests to declare and no further financial disclosures to make. JB and WL have received grant research support from Danone Nutricia Early Life Nutrition. CC has received consultancy, lecture fees and honoraria from AMGEN, GSK, Alliance for Better Bone Health, MSD, Eli Lilly, Pfizer, Novartis, Servier, Medtronic and Roche. The study described in this manuscript is not related to these relationships.

  • Patient consent for publication Not required.

  • Ethics approval Ethical approval for the WRAPPED study has been obtained from the University of Southampton, Faculty of Medicine Ethics Committee (ID 20986.A4).

  • Provenance and peer review Not commissioned; peer reviewed for ethical and funding approval prior to submission.

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