Interactive Conversational Agents to Improve Dietary Behaviors for Health Promotion: Mixed Systematic Review.

Background: Chronic diseases are the leading global cause of death, largely driven by Western lifestyles characterized by poor diets and physical inactivity. Digital interventions offer promising tools to support health behavior change. Interactive conversational agents (CAs) provide real-time, personalized meal planning and dietary advice. Their interactive nature and adaptability make them valuable for promoting healthy dietary behaviors in the context of diet-related chronic diseases. However, evidence of their effectiveness remains limited. Systematic evaluations of their impact, features, and user acceptability are needed to clarify their role in public health strategies for improving dietary behaviors and preventing chronic diseases. Objective: This review aimed to evaluate the effectiveness of CAs in improving dietary behaviors, to describe their features, functions, conversational capabilities, and impact on nutritional knowledge, usability, acceptability, user experience, and engagement. Methods: Five electronic databases were searched: MEDLINE, CINAHL, Embase, Web of Science, and PsycINFO. We only included sources that focused on the use of CAs to change dietary behavior. Eligible studies were published since 2013 in English, French, or Spanish. Two independent reviewers screened studies, with a third resolving disagreements. The quality of studies was appraised using the Mixed Methods Appraisal Tool (McGill University). Quantitative and qualitative findings were synthesized narratively. Results: In total, 2200 references were identified, and after screening and eligibility assessment, 11 references (10 studies with approximately 20-480 participants) were included. Among the included studies, improvements in fruit and vegetable intake were reported in 2 studies (P=.04 and P=.005). One study found significant increases in adherence to the Mediterranean diet at 6 weeks with gains maintained at 12 weeks. Two additional studies reported enhanced nutritional knowledge (eg, nutrition label use). Effects on protein, whole grains, sugar, sodium, and caffeine intake were mixed or nonsignificant. Some studies reported increased physical activity (+109.8 min/wk) and reduced alcohol use for stress management. One randomized controlled trial showed modest but significant weight loss and decrease in waist circumference (-2.1 cm, 95% CI -3.5 to 0.7; P=.003). Engagement varied between studies. Usability and user experience were generally positive; goal setting, feedback, and tailored recommendations were linked to higher satisfaction. Reported challenges included unnatural conversation style, simplistic content, and limited perceived usefulness. Conclusions: CAs show promising potential to improve dietary behaviors, with evidence of gains in fruit and vegetable intake, Mediterranean diet adherence, nutritional knowledge, physical activity, and modest weight loss. Overall usability was favorable, but variability in outcomes, high attrition, and limited impact on social support highlight areas for refinement. Future research should use larger samples, longer follow-up, standardized outcomes, and strategies to enhance sustained engagement and inclusivity. Systematic evaluations and refined designs are essential to establish the role of CAs as scalable, evidence-based tools in chronic disease prevention.