Randomised Controlled Trial to reduce unhealthy snacking: evaluation of planning tools and method of allocation in a sample with diverse health literacy and diabetes or high BMI

This study is testing the effects of two intervention factors, all conducted online through a survey platform: 1) Allocation method 2) Type of action plan Allocation method: Arm 1: Random (Arm A) Arm 2: Screening (Arm B) Arm 3: Choice (Arm C) Type of action Plan Arm 1: literacy sensitive action plan (labelled for participants as Smart Snacking 101 (basic plan)) Arm 2: standard action plan (labelled for participants as "Smart Snacking Pro (advanced plan)) ALLOCATION METHODS 1. RANDOM (Arm A): Participants randomised to the ‘random’ arm will be further randomised to either 1) assess their prior preferences (i.e. their preferred action plan; Arm A1), and then randomised to the standard or literacy-sensitive action plan; or 2) randomised to the standard or literacy-sensitive action plan without assessment of prior preferences (Arm A2). Prior preference will be measured using the same format as in the ‘participant choice’ arm (Arm C) with additional text stating that participants may not receive their preferred tool. 2. SCREENING (Arm B): Allocation is based on health literacy (NVS) scores. Those scoring less than 4 (scores indicative of inadequate health literacy) were allocated to the literacy sensitive action plan, and the remaining participants were allocated to the standard action plan. Participants will be told that, based on their responses, the researchers have selected an action plan tool that is most suitable for them. 3. CHOICE (Arm C): Participants are provided with a brief description of the action plans and select the plan they will use. Participants have the option of selecting ‘Unsure’ to allow for undecided participants. Participants will then be presented with an alternative description of the study and asked again to make a choice. Participants will be informed that if they select ‘Unsure’ again, the researchers will select a plan for them. In doing so, participants will be randomised to an action plan. TYPE OF ACTION PLAN: 1. LITERACY SENSITIVE ACTION PLAN: This commences with the text: “We want you to plan how you will change your unhealthy snacking behaviour each day because forming plans has been shown to improve snacking habits”. The intervention consists of 4 steps that guide the user through the process of developing an appropriate plan: a. Step1: Sometimes we snack because we are hungry, but there are lots of other reasons too. Think about your snacks in the last week. Below is a list of ‘snack moments.’ These are times when people tend to choose unhealthy snacks or eat too much. Choose 3 snack moments from the list that happened to you the most often in the last week. [List of snack moments]. b. Step 2: Below are your top 3 snack moments. Some snack moments will be more important than others. Choose the 1 that you would be happiest to change. [User chooses from 3 previously selected snack moments] c. Step 3: Great! Your most important snack moment was snacking because you are bored. The last step is to come up with a plan! Choose the solution that you think will work best for you. Drag it into the space on the right. [List of solutions] d. Step 4: Imagine how your plan might feel.[examples of scenarios when this might happen]. The final step is to make sure the plan is realistic. How hard do you think it will be to do this plan for the next month [Slider from very easy to very hard. If the user selects a number greater than or equal to 7 they will be prompted to revise the plan] 2. STANDARD ACTION PLAN (instructions): We want you to plan how you will change your unhealthy snacking behaviour each day because forming plans has been shown to improve snacking habits. You are free to choose how you do this but we want you to formulate your plans in as much detail as possible. Pay attention to the situations in which you will implement (carry out) these plans. Focus on situations when you are not hungry but find yourself snacking. For both types of action plan interventions, immediately before submitting the baseline survey, participants will be presented with their plan a final time, instructed to write down, take a screenshot or make a copy of it, and will be asked to indicate that they have a copy of the plan. All participants will be emailed a reminder of their personal plan at baseline (within the first week), and before then end of the 2nd and 3rd weeks. Participants will complete a follow-up survey after 4 weeks. Both interventions will be administered using an online survey hosted by Qualtrics. At no point do participants have any direct interaction from researchers. Email reminders will be automated using a mail merge function. The baseline intervention will be delivered initially over a short period (approximately 1 week) in order to ascertain that the survey is collecting data correctly with a smaller number of participants (N=~200). As the sample size estimation assumes an equal proportion of participants choosing the literacy sensitive and standard action plans in the choice arm, and an equal proportion of participants identified as having low and high health literacy in the screening arm, at this point these proportions will be calculated. If it is found that these proportions are substantially different from 50%, the sample size will be adjusted to ensure adequate power is maintained. After these participants are recruited, further recruitment will be paused until follow up data is collected from this initial sample, again to ensure that the survey is correctly collecting data. We expect that recruitment of the remaining participants could be completed within a period of 3 weeks. Adherence to the intervention in both action planning groups will be ensured by forcing a response for items that help the participant to create their plan. Coding (see analysis section) of standard action plans will assess adherence to the intervention.