Diet Improvement Through Normative Experimentation

Not Applicable

Completed

• Conditions: Diet Quality
• Interventions: Behavioral: Norm-based messaging and peer comparison features; Behavioral: Financial Incentives leveraging on loss aversion

• Registration Number: NCT05070442
• Lead Sponsor: Duke-NUS Graduate Medical School

Brief Summary

This study aims to use a three-arm randomized control trial (RCT) implemented in a fully functional experimental online grocery store, to explore the effects of two low-cost information and incentive-based strategies. These strategies comprise of injunctive norm-based messaging and the use of financial incentive leveraging on loss aversion to encourage the purchase of healthy foods. The investigators have set up a store wherein products may be purchased by participants and subsequently delivered to homes in some of the conditions. This increases the external validity of these interventions and enables investigators to establish greater confidence in their generalizability.

Detailed Description

The Asia-Pacific is faced with an epidemic of rising rates of chronic disease. Poor diet quality is a demonstrated risk factor for non-communicable diseases. Excess intake of calories, saturated fat and sodium increases the risk of obesity, heart disease, diabetes, and other chronic conditions.

Behavioral economics has emerged as a promising strategy to increase the effectiveness of interventions aimed to address risk factors for non-communicable diseases (NCDs). Yet, there is a gap in knowledge concerning how norm-based messaging and peer influence interventions can be implemented to improve diet quality.

Using a three-arm randomized trial with a 3x3 crossover design, investigators aim to determine whether norm-based messaging and peer comparisons, with or without financial incentives, improve diet quality.

Each participant will be exposed to all of the following intervention arms in random order:

Arm 1: Control arm. Participants will experience an unmodified version of NUSMart which replicates the traditional shopping experience of online grocery stores.

Arm 2: Participants will experience a modified version of NUSMart with norm-based messaging and peer comparison features enabled. Nutri-Score labels will be enabled and displayed on all products within the store. A floating side panel will provide a visual indicator of the participants' average weighted Nutri-Score.

Arm 3: Same as Arm 2, except participants are notified of an additional $5 reward towards participation reimbursement. However, this additional $5 will be forfeited if the basket average weighted Nutri-Score falls below the average of participants' peers'. (Financial incentive leveraging on loss aversion).

Investigators hypothesize the following:

Primary hypothesis: Diet quality, as measured by mean Nutri-Score weighted by number of servings of all basket items, will be greatest when exposed to the intervention with norm-based messaging with incentive (Arm 3), followed by the intervention with norm-based messaging without the incentive (Arm 2), followed by Control (Arm 1).

Investigators will test this hypothesis in total, and separately for foods and beverages given Singapore's focus on reducing intake of sugar-sweetened beverages.

Study Timeline

• Study First Submitted: 2021-09-20
• Study First Submitted QC: 2021-10-03
• Study First Posted: 2021-10-07
• Study Start: 2022-04-22
• Primary Completion: 2022-10-26
• Study Completion: 2022-10-26
• Status Verified: 2023-02
• Last Update Submitted: 2023-02-13
• Last Update Posted: 2023-02-15

Recruitment & Eligibility

• Status: COMPLETED
• Sex: All
• Target Recruitment: 248

Inclusion Criteria

• Singapore resident
• Age 21 and above
• Must be the primary weekly grocery shopper in their household

Exclusion Criteria

• Non-Singapore resident
• Non-primary grocery shopper in their household
• Less than 21 years old

Study & Design

• Study Type: INTERVENTIONAL
• Study Design: CROSSOVER

Arm && Interventions

Group	Intervention	Description
Norms and Incentive Arm (Arm 3)	Norm-based messaging and peer comparison features	Same as Arm 2, except participants are notified that they have been awarded an additional $5 towards their participation reimbursement. However, this additional $5 will be forfeited if their basket average weighted Nutri-Score falls below the average of their peers'. (Financial incentive leveraging on loss aversion).
Norms Arm (Arm 2)	Norm-based messaging and peer comparison features	Participants will experience a modified version of NUSMart with norm-based messaging and peer comparison features enabled. Nutri-Score labels will be enabled and displayed on all products within the store. A floating side panel will provide a visual indicator of the participants' average weighted Nutri-Score.
Norms and Incentive Arm (Arm 3)	Financial Incentives leveraging on loss aversion	Same as Arm 2, except participants are notified that they have been awarded an additional $5 towards their participation reimbursement. However, this additional $5 will be forfeited if their basket average weighted Nutri-Score falls below the average of their peers'. (Financial incentive leveraging on loss aversion).

Primary Outcome Measures

Name	Time	Method
Diet Quality	After completion of data collection, an average of about 5 months	Diet quality, as measured by raw Nutri-Score points (-15 to 40) weighted by number of servings of all basket items. Here, a smaller value means a better outcome. Raw Nutri-Score is measured according to the guidelines from the Sante Publique France.

Secondary Outcome Measures

Name	Time	Method
Average Nutri-Score	After completion of data collection, an average of about 5 months	Average Nutri-Score (1 to 5) weighted by number of servings of all basket items. Here, a higher value means a better outcome. This is calculated by converting Nutri-Score letters to numbers such that Nutri-Score E is 1, D is 2 and so on till Nutri-Score A which is 5.
Average Sodium	After completion of data collection, an average of about 5 months	Average sodium per shopping trip.
Average Saturated Fat	After completion of data collection, an average of about 5 months	Average saturated fat per shopping trip.
Average Calories	After completion of data collection, an average of about 5 months	Average calories per shopping trip.
Average Sugar	After completion of data collection, an average of about 5 months	Average sugar per shopping trip.
Average Fat	After completion of data collection, an average of about 5 months	Average fat per shopping trip.

Trial Locations

Locations (1)

Duke-NUS Graduate Medical School; 🇸🇬 Singapore, Singapore