Document Type

Article

Publication Date

7-11-2026

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This article is the author’s final published version in Annals of Behavioral Medicine, Volume 60, Issue 1, 2026, Article number kaag038.

The published version is available at https://doi.org/10.1093/abm/kaag038. Copyright © The Author(s) 2026.

 

Abstract

Background: Approximately 2 billion adults seek lifestyle modification to improve their health and well-being. However, because of cost and access barriers, only a tiny fraction receive gold-standard lifestyle modification programs led by trained coaches. Digital programs without human coaches are more disseminable but have limited efficacy. Recent advances in large language model (LLM) AI chatbots have the potential to revolutionize digital programs by emulating human coaches, offering a safe, low-cost, and scalable lifestyle modification intervention. Yet, no studies have developed and tested such a program. Purpose: This study aims to evaluate the feasibility, safety, and user engagement of a new AI chatbot-powered lifestyle modification program named Lyra, which utilizes recent advances in LLM technology to potentially emulate the benefits of human coaching. Methods: We developed Lyra, which integrates structured psychoeducational programming, digital tracking of health behaviors, and text messaging, all powered by an LLM engine. We tested the 8-week program, which included interactive training in behavioral strategies, customized meal plans, tailored feedback on goal progress, and on-demand coaching, with 17 participants in a sample of participants with overweight/obesity seeking lifestyle modification. Results: The program was successfully implemented at a cost of $1.78/participant/week. Coders rated 2288 messages from and 475 conversations with Lyra. All were deemed safe, and the mean expertise was 8.5/10. Participants (mean BMI = 31.5) rated Lyra as helpful (69%), empathic (88%), and easy to use (94%); 88% valued having 24-h availability, and 75% developed a connection to Lyra. Participants initiated an average of 6.2 conversations, ranging from coping with cravings to unprompted “confessions” of having consumed unhealthy food. Conclusion: This new form of intervention proved feasible, acceptable, safe, clinically adept, and capable of fostering a connection. However, rigorous testing of Lyra’s effectiveness is necessary.

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Creative Commons License
This work is licensed under a Creative Commons Attribution-Noncommercial 4.0 License

Language

English

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