INTRODUCTION: With the growing use of GLP-1/GIP receptor agonist medications, their impact on dietary intake and quality remains unclear. This systematic review examined how randomized controlled trials (RCT) prescribing liraglutide, semaglutide, or tirzepatide assessed and reported dietary intake and quality as outcome measures, alongside weight loss and/or glycemic control, and identified gaps in the use and methodological quality of dietary assessment methods.

METHODS: Medline, Embase, Cochrane, Scopus, and CINAHL were systematically searched between January 2008-January 2025 (adults) and January 2014-January 2025 (children/adolescents). The review was registered with the Open Science Framework (DOI: 10.17605/OSF.IO/XPNGY).

RESULTS: Forty-three articles from 41 unique RCTs, comprising 50,690 participants (n = 688 children/adolescents, n = 50,002 adults) were included. Except for two studies targeting adults (one published and one unpublished data from an included study), this review found no other studies that assessed or reported dietary intake or changes in diet. Both reported a reduction in the total energy intake and altered macronutrient distribution in the medication plus diet group, although one was not significantly different from medication alone. Quality of assessment methods used was categorized as "poor" and "acceptable," respectively. These results highlight a critical gap in the literature.

CONCLUSION: Only 2/41 studies (≈5%) reported or assessed dietary intake or evaluated diet changes secondary to GLP-1/GIP RA medication use. This review highlights a major gap in the evidence requiring urgent attention. More high-quality research, using validated dietary assessment methods as outcome measures in RCTs is needed to understand how these medications impact diet and diet quality, nutrient intake, and chronic disease risk.