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Improving body image at scale among Brazilian adolescents: Study protocol for the co-creation and randomised trial evaluation of a chatbot intervention

Matheson, Emily; Smith, Harriet; Amaral, Ana; Meireles, Juliana; Almeida, Mireille; Mora, G.; Leon, Camilo; Gertner, Gaston; Ferrario, Nico; Suarez Battan, Lu; Linardon, Jake; Fuller-Tyszkiewicz, Matthew; Diedrichs, Phillippa


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Dr Emily Matheson
Senior Research Fellow (Centre for Appearance Research)

Ana Amaral

Juliana Meireles

Mireille Almeida

G. Mora

Camilo Leon

Gaston Gertner

Nico Ferrario

Lu Suarez Battan

Jake Linardon

Matthew Fuller-Tyszkiewicz


Background: Body image concerns are prevalent among Brazilian adolescents and can lead to poor psychological and physical health. Yet, there is a scarcity of culturally-appropriate, evidence-based interventions that have been evaluated and made widely available. Chatbot technology (i.e., software that mimics written or spoken human speech) offers an innovative method to increase the scalability of mental health interventions for adolescents. The present protocol outlines the co-creation and evaluation of a body image chatbot for Brazilian adolescents via a partnership between academics, industry organisations and the United Nations Children’s Fund (UNICEF).
Methods: A two-armed fully remote randomised controlled trial will evaluate the chatbot’s effectiveness at improving body image and well-being. Adolescent girls and boys (N = 2,800) aged 13-18 years recruited online will be randomly allocated (1:1) into either: 1) a body image chatbot or 2) an assessment-only control condition. Adolescents will engage with the chatbot over a 72-hour period on Facebook Messenger. Primary outcomes will assess the immediate and short-term impact of the chatbot on state- and trait-based body image, respectively. Secondary outcomes will include state- and trait-based affect, trait self-efficacy and treatment adherence.
Discussion: This research is the first to develop an evidence-informed body image chatbot, with the proposed efficacy trial aiming to provide support for accessible, scalable and cost-effective interventions that address disparities in body image prevalence and readily available resources.
Trial registration number: NCT04825184, registered 30th March 2021 (website:


Matheson, E., Smith, H., Amaral, A., Meireles, J., Almeida, M., Mora, G., …Diedrichs, P. (2021). Improving body image at scale among Brazilian adolescents: Study protocol for the co-creation and randomised trial evaluation of a chatbot intervention. BMC Public Health, 21(1), Article 2135.

Journal Article Type Article
Acceptance Date Oct 29, 2021
Online Publication Date Nov 20, 2021
Publication Date Nov 20, 2021
Deposit Date Nov 15, 2021
Publicly Available Date Dec 15, 2021
Journal BMC Public Health
Electronic ISSN 1471-2458
Publisher BioMed Central
Peer Reviewed Peer Reviewed
Volume 21
Issue 1
Article Number 2135
Keywords Adolescent; body image; mental health; chatbot; micro-intervention; Brazil; low- and middle-income countries; randomised controlled trial; study protocol
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