Plain English Summary
Background and study aims
People in the UK consume far too much sugar, exceeding recommendations, with the largest source in the diet being sugar-sweetened beverages (SSBs). SSB consumption has been linked with health problems, including the development of obesity (being very overweight), metabolic syndrome (where someone is obese, has diabetes and high blood pressure), diabetes, and dental disease. It also contributes to health inequalities given that people who are more socially deprived consume more SSBs. One possible way of reducing SSB consumption is to reduce the sizes of the containers (i.e. bottles and cans) in which these drinks are available. However, there is currently no evidence that this would reduce SSB consumption. The aim of this study is to find out whether placing a fixed volume of SSBs in smaller bottle sizes reduces consumption at home.
Who can participate?
Households (defined as people who live together, who may or may not be related but who share all or most drink and food within the house) that buy at least 2 litres of week of regular (i.e. not diet or low sugar) cola drinks and live in Cambridge, UK
What does the study involve?
Each week, for four weeks, the research team give each participating household a set amount of a carbonated cola drink based on how much cola they typically buy in a week. The total amount of cola is split into bottles of one of four sizes: 1500ml, 1000ml, 500ml or 250ml. All the cola delivered in a week to particular household is in the same sized bottle. Each household is also given their cola in each of the four bottle sizes over the 4-week period of the study.
What are the possible benefits and risks of participating?
The findings from this preliminary study will help to design a larger study to test whether giving a fixed amount of SSBs in smaller bottle sizes reduces consumption at home. The results are expected to contribute to ongoing scientific and policy discussions about effective methods for reducing sugar intake in the general population. This study is considered to be low risk. No adverse consequences are expected.
Where is the study run from?
The Behaviour and Health Research Unit at the University of Cambridge (UK)
When is the study starting and how long is it expected to run for?
May 2015 to June 2016
Who is funding the study?
Department of Health Policy Research Programme (Policy Research Unit in Behaviour and Health [PR-UN-0409-10109])
Who is the main contact?
Prof. Theresa Marteau
Impact of bottle size on in-home consumption of sugar-sweetened beverages (SSBs): a feasibility and acceptability study
The impact on consumption of altering the available sizes of the containers in which SSBs are presented is not known. We are planning a cross-over randomised controlled trial to assess the impact of presenting a fixed volume of SSBs in different bottle sizes on consumption within homes. This will provide evidence to assess the potential of reductions in package size to decrease consumption and test the hypothesis that smaller package size reduces consumption. Prior to conducting this trial we need to reduce some key uncertainties related to the study design. The aim of this study is to assess the feasibility and acceptability of the procedures for recruitment, allocation, measurement, retention and intervention delivery of the aforementioned randomised controlled trial.
University of Cambridge Psychology Research Ethics Committee, 15/03/2015, ref: Pre.2015.20
Feasibility cross-over randomised controlled trial using a mixed methods design conducted in home settings
Primary study design
Secondary study design
Randomised cross over trial
Patient information sheet
Not available in web format, please use contact details to request a participant information sheet
High consumption of sugar-sweetened beverages (SSBs), which has been associated with weight gain and the development of non-communicable diseases including diabetes and poor oral health.
Receipt of a given quantity of a carbonated cola sugar-sweetened beverage for consumption at home but sub-divided into bottles of one of four different sizes:
1. In 1500 millilitre bottles
2. In 1000 millilitre bottles
3. In 500 millilitre bottles
4. In 250 millilitre bottles
In any one week households will receive cola in just one size of bottle, with the number of bottles being determined by the total volume of cola each household receives; this will be fixed across all four intervention periods. This fixed volume will be determined with reference to the volume of cola households purchased during a two-week baseline period, as assessed by till receipts and by self-report, rounded up to the nearest multiple of three litres. Volumes consisting of multiples of three litres are needed to avoid the total quantity varying systematically between intervention periods, thereby confounding the effect of altering the bottle size with volume. During each intervention week, households will be given the opportunity to receive additional deliveries should they want these. All participating households will receive all interventions according to a pre-specified random order.
Primary outcome measures
This feasibility study is not powered to detect changes in outcome measures but to assess feasibility and acceptability of procedures planned for a full-scale trial.
1. Recruitment rates
2. Number of households discontinuing participation at follow-ups
3. Awareness of the study aim, assessed through i) questionnaire and ii) qualitative interviews
4. Practical problems associated with:
4.1. The randomisation procedure
4.2. Delivering the intervention
4.3. Collection of consumption-related data
Acceptability outcomes assessed through qualitative interviews
1. Acceptability of the:
1.2. Study procedures
1.3 Assessment procedures
1. Characteristics of participating households, assessed through questionnaire:
1.1. Index of Multiple Deprivation scores (derived from postcodes)
1.2. Total household income
1.3. Household composition (number of adults; number of children)
1.4. Highest education qualification obtained by any person within the household
1.5. Gender of all household members
1.6. Age of all household members
2. Volume of cola in millilitres consumed by the household during each of the week-long intervention periods, measured:
2.1. Objectively, by recording the numbers of empty and remaining full bottles. The remaining volume of partly consumed bottles will be measured using a measuring jug.
2.2. Subjectively, through self-report via questionnaire
Secondary outcome measures
Overall trial start date
Overall trial end date
Participant inclusion criteria
Participating households will be of any size or composition. Households are defined as people who live together, who may or may not be related but who share all or most drink and food within the house. This includes households consisting of:
1. Single members
2. Couples (married or cohabitating)
3. Families with school age children
4. Single parents with dependent children
5. Families with extended family members living in the house (e.g. grandparents)
Multi-occupancy households comprising non-related individuals are excluded. Inclusion criteria for participating households are as follows:
1. Purchase regular (not low sugar) Coca-Cola® or Pepsi Cola® at a minimum rate of two litres a week
2. Reside in or near to Cambridge, UK, within 10 miles of the research team base
3. Do not plan to be away from home for longer than seven days during the study period
Target number of participants
100 eligible households will initially be approached with the aim of assessing (a) how many are interested in taking part in the study and (b) how many complete a one-week run in period (an indicator of active participation for one week). Of the households completing the run-in period and expressing a willingness to continue with the study, 16 will be invited to continue their participation. If fewer than 16 households complete the run-in period, additional households will be approached. One individual will be recruited from each eligible household to act as a household representative, who will consent to participation in the study on behalf of all household members and provide all necessary data.
Participant exclusion criteria
1. Households not located in Cambridge, UK
2. Households consuming less that two litres of cola per week
3. Households consuming cola brand other than Pepsi Cola® or Coca-Cola® or diet/sugar free versions of the included brands.
Recruitment start date
Recruitment end date
Countries of recruitment
Trial participating centre
Behaviour and Health Research Unit
University of Cambridge Institute of Public Health Forvie Site
Department of Health Policy Research Programme (UK)
Funding Body Type
Funding Body Subtype
Results and Publications
Publication and dissemination plan
IPD sharing statement
The datasets generated during and/or analysed during the current study are/will be available upon request from Saphsa Codling (firstname.lastname@example.org)
Intention to publish date
Participant level data
Available on request
Results - basic reporting