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Research Christmas 2018: Food For Thought

Effectiveness of a brief behavioural intervention to prevent weight gain over the Christmas holiday period: randomised controlled trial

BMJ 2018; 363 doi: (Published 10 December 2018) Cite this as: BMJ 2018;363:k4867

Linked Editorial

Bringing harmony to public health debates about food

  1. Frances Mason, PhD candidate1,
  2. Amanda Farley, lecturer in public health and epidemiology1,
  3. Miranda Pallan, senior clinical lecturer in public health1,
  4. Alice Sitch, lecturer in biostatistics1 2,
  5. Christina Easter, medical statistician1,
  6. Amanda J Daley, professor of behavioural medicine3
  1. 1Institute of Applied Health Research, University of Birmingham, Birmingham B15 2TT, UK
  2. 2NIHR Birmingham Biomedical Research Centre, University Hospitals Birmingham NHS Foundation Trust and University of Birmingham, UK
  3. 3School of Sport, Exercise and Health Sciences, Loughborough University, Loughborough, Leicestershire, UK
  1. Correspondence to: A Farley a.c.farley{at}
  • Accepted 12 November 2018


Objective To test the effectiveness of a brief behavioural intervention to prevent weight gain over the Christmas holiday period.

Design Two group, double blinded randomised controlled trial.

Setting Recruitment from workplaces, social media platforms, and schools pre-Christmas 2016 and 2017 in Birmingham, UK.

Participants 272 adults aged 18 years or more with a body mass index of 20 or more: 136 were randomised to a brief behavioural intervention and 136 to a leaflet on healthy living (comparator). Baseline assessments were conducted in November and December with follow-up assessments in January and February (4-8 weeks after baseline).

Interventions The intervention aimed to increase restraint of eating and drinking through regular self weighing and recording of weight and reflection on weight trajectory; providing information on good weight management strategies over the Christmas period; and pictorial information on the physical activity calorie equivalent (PACE) of regularly consumed festive foods and drinks. The goal was to gain no more than 0.5 kg of baseline weight. The comparator group received a leaflet on healthy living.

Main outcome measures The primary outcome was weight at follow-up. The primary analysis compared weight at follow-up between the intervention and comparator arms, adjusting for baseline weight and the stratification variable of attendance at a commercial weight loss programme. Secondary outcomes (recorded at follow-up) were: weight gain of 0.5 kg or less, self reported frequency of self weighing (at least twice weekly versus less than twice weekly), percentage body fat, and cognitive restraint of eating, emotional eating, and uncontrolled eating.

Results Mean weight change was −0.13 kg (95% confidence interval −0.4 to 0.15) in the intervention group and 0.37 kg (0.12 to 0.62) in the comparator group. The adjusted mean difference in weight (intervention−comparator) was −0.49 kg (95% confidence interval −0.85 to −0.13, P=0.008). The odds ratio for gaining no more than 0.5 kg was non-significant (1.22, 95% confidence interval 0.74 to 2.00, P=0.44).

Conclusion A brief behavioural intervention involving regular self weighing, weight management advice, and information about the amount of physical activity required to expend the calories in festive foods and drinks prevented weight gain over the Christmas holiday period.

Trial registration ISRCTN Registry ISRCTN15071781.


  • Contributors: AJD conceived the study with input from AF. AJD wrote the protocol with contributions from AF and FM. FM wrote the first version of the manuscript with input from coauthors. FM, AJD, AF, and MP wrote the statistical analysis plan with input from AS and CE. CE conducted the statistical analyses with support from AS. All authors had full access to the data, take responsibility for the integrity of the data and the accuracy of the data analysis, contributed to the interpretation of the results, and reviewed and approved the final manuscript. AJD is the guarantor. The corresponding author attests that all listed authors meet authorship criteria and that no others meeting the criteria have been omitted.

  • Funding: This work was independent research as part of a PhD studentship funded by the School of Medical and Dental Sciences at the University of Birmingham. This paper presents independent research supported by the National Institute for Health Research (NIHR) Birmingham Biomedical Research Centre at the University Hospitals Birmingham NHS Foundation Trust and the NIHR Leicester Biomedical Research Centre. The views expressed are those of the authors and not necessarily those of the NHS, the NIHR, or the Department of Health.

  • Competing interests: All authors have completed the ICMJE uniform disclosure form at and declare: no support from any organisation for the submitted work; no financial relationships with any organisations that might have an interest in the submitted work in the previous three years, no other relationships or activities that could appear to have influenced the submitted work. AF reports grants from Ethicon (Johnson and Johnson), researcher led, outside the submitted work.

  • Ethical approval: This study was approved by the University of Birmingham Science, Technology, Engineering and Mathematics ethical review committee (ERN_16-0673). All participants provided written informed consent.

  • Data sharing: Data from the Winter Weight Watch study or the study materials are available from the corresponding author at All individual participant data will be available on request one year after publication of trial outcomes. The study protocol is available on request. All requests for data access will need to specify the planned use of data and will require approval from the trial investigator team prior to release.

  • Transparency: The guarantor (AJD) affirms that this manuscript is an honest, accurate, and transparent account of the study being reported; that no important aspects of the study have been omitted; and that any discrepancies from the study as planned have been explained. The manuscript follows the CONSORT guidelines for the reporting of clinical trials.

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