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Nudges to improve healthy food consumption in large supermarkets

Last registered on December 02, 2020


Trial Information

General Information

Nudges to improve healthy food consumption in large supermarkets
Initial registration date
November 26, 2020

Initial registration date is when the trial was registered.

It corresponds to when the registration was submitted to the Registry to be reviewed for publication.

First published
November 30, 2020, 11:36 AM EST

First published corresponds to when the trial was first made public on the Registry after being reviewed.

Last updated
December 02, 2020, 12:33 PM EST

Last updated is the most recent time when changes to the trial's registration were published.



Primary Investigator

Departament of Economics School of Social Sciences

Other Primary Investigator(s)

PI Affiliation
Universidad de Montevideo
PI Affiliation
Universidad de la República
PI Affiliation
Cornell University

Additional Trial Information

Start date
End date
Secondary IDs
The aim of this project is to evaluate the use of nudges to improve households’ food choices towards healthier options in a real shopping framework. Data for the analysis come from a big supermarket that keeps track of purchases made by clients who are members of its loyalty program. We hypothesize that customers will improve the nutritious quality of food choices when provided with weekly messages reminding them about the importance of eating healthy food, suggesting simple ways to include them in the family’s menu, and encouraging them to take these tips into action. In particular, messages designed to highlight and promote the consumption of fruits, vegetables, grains, seeds, nuts, legumes and fish, and cooking at home, are expected to have an impact on the composition of grocery purchases, increasing items promoted and reducing less healthy food choices.
External Link(s)

Registration Citation

Balsa, Ana et al. 2020. "Nudges to improve healthy food consumption in large supermarkets." AEA RCT Registry. December 02.
Sponsors & Partners

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Experimental Details


We send text messages to frequent buyers of a large grocery store with the aim of promoting healthy food consumption among consumers and changing purchasing patterns towards healthier products. The messages combine the delivery of relevant nutritional information in small doses with simple tips and suggestions (including video recipes) to facilitate the incorporation of healthier habits. The design of the messages aims at reoptimizing consumers' choice architecture by counteracting the influence of present bias, cognitive fatigue, and unhealthy environments. We send messages 3 times a week for 9 weeks.
Intervention Start Date
Intervention End Date

Primary Outcomes

Primary Outcomes (end points)
Purchases of promoted (healthy) and non-healthy food choices. Healthy items that were promoted in the intervention include fruits, vegetables, grains, seeds, nuts, legumes, and fish.
Primary Outcomes (explanation)
We will construct an aggregate index quantifying the nutrition content of food purchases.

Secondary Outcomes

Secondary Outcomes (end points)
Secondary Outcomes (explanation)

Experimental Design

Experimental Design
Customers within the “best customers” and “best customers with potential” categories were contacted by the supermarket by email. They were invited to give an informed consent and asked to fill a short survey that provided basic data about family composition, consumption habits and products commonly purchased in the supermarket. Between September and November 2019 we recruited a large group of clients (group 1) and during June 2020 we recruited a second group of clients (group 2).

In both groups we randomized clients to a treatment and a control arm. Clients in the treatment groups received messages through WhatsApp over a period of nine weeks regarding the following subjects: cooking at home, vegetables, fruits, healthy snacks, mindful eating, legumes, fish, and healthy eating. Clients in group 1 received messages between June 13th and September 24th 2020, while clients in group 2 received messages between August 11th and October 8th 2020.
Experimental Design Details
Randomization Method
Randomization done in office using STATA.
Randomization Unit
Was the treatment clustered?

Experiment Characteristics

Sample size: planned number of clusters
2140 individuals
Sample size: planned number of observations
2140 individuals (supermarket clients)
Sample size (or number of clusters) by treatment arms
1074 assigned to treatment group and 1066 to control group
Minimum detectable effect size for main outcomes (accounting for sample design and clustering)

Institutional Review Boards (IRBs)

IRB Name
Comité de ética - Universidad de Montevideo
IRB Approval Date
IRB Approval Number


Post Trial Information

Study Withdrawal

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Is the intervention completed?
Intervention Completion Date
September 15, 2020, 12:00 +00:00
Data Collection Complete
Data Collection Completion Date
December 31, 2020, 12:00 +00:00
Final Sample Size: Number of Clusters (Unit of Randomization)
1590 customers
Was attrition correlated with treatment status?
Final Sample Size: Total Number of Observations
1590 customers
Final Sample Size (or Number of Clusters) by Treatment Arms
791 customers in treatment group
Data Publication

Data Publication

Is public data available?

Program Files

Program Files
Reports, Papers & Other Materials

Relevant Paper(s)

Reports & Other Materials