Toward standardized personalized nutrition: a methodological scoping review and meta-analysis of randomized controlled trials in adults with overweight and obesity

Personalized nutrition (PN) interventions are increasingly used to address overweight and obesity, yet randomized controlled trials (RCTs) vary widely in how personalization is defined and delivered. This scoping review synthesized methodological characteristics of PN RCTs in adults with overweight or obesity and meta-analyzed PN effects on anthropometrics. We searched PubMed, Scopus, Web of Science, and ClinicalTrials.gov through November 20, 2025. Data were extracted using a standardized template capturing intervention characteristics. A random-effects meta-analysis was conducted, Bayesian meta-regression was used to explore the effect of intervention duration, and certainty of evidence was evaluated using GRADE. Among the 17 included RCTs, none provided a definition of PN, and substantial methodological heterogeneity was evident. Personalization inputs differed markedly in both number and type, and delivery modes ranged from digital platforms and group sessions to meal-box provision and routine dietitian consultations. PN interventions typically used the same delivery format as their control groups but layered on individualized components, with some providing higher contact frequency. Comparator structures also varied, from standardized guideline-based diets to minimal or no dietary counseling. Personalized diets were produced through algorithmic models, dietitian-guided tailoring, or continuous glucose monitoring-guided participant selection. PN produced a small but significant reduction in body weight, while effects on body mass index (BMI) were non-significant. Longer intervention duration was credibly associated with greater reductions in body weight and BMI. No publication bias was detected, and certainty of evidence was low for body weight and very low for BMI. PN interventions show modest effects on body weight but not BMI, within a highly heterogeneous methodological landscape. This review identifies design features to guide more effective PN interventions. Advancing toward more standardized approaches will require clearer operational definitions of personalization, better-aligned comparator diets, and greater transparency in how personalized strategies are generated and delivered.