Relationship between Vitamin D Status and the Risk of Obesity without Diagnosed Metabolic Syndrome: A Meta-Analysis of Observational Studies

BACKGROUND: The association between daily vitamin D (VD) intake and the risk of healthy obesity remains controversial. METHODS: PubMed, Embase, Web of Science, Wanfang Database, China Science and Technology Periodical Database, and the Cochrane Database of Systematic Reviews were systematically searched for published observational studies up to January 2025. Ultimately, 74 studies were included, and pooled estimates were obtained using RevMan version 5.3. Subgroup analyses were conducted by age, VD detection method and assessment criteria, and obesity grade. RESULTS: Among 5,283 articles identified, 74 studies with 110,838 individuals met the inclusion criteria. Serum/plasma 25-hydroxyvitamin D concentrations were negatively associated with the risk of healthy obesity (mean difference=-3.98; 95% confidence interval [CI], -4.70 to -3.27). Significant differences between the obesity and control groups were observed in all subgroups except those using liquid chromatography-tandem mass spectrometry/mass spectrometry (LC-MS/MS) detection. Moreover, the prevalence of VD deficiency was higher in participants with obesity than in controls (odds ratio [OR], 2.02; 95% CI, 1.73 to 2.36). This difference was significant in all subgroups except those in which VD deficiency was defined as a concentration below 10 or 12 ng/mL. Furthermore, VD insufficiency was positively associated with the risk of obesity (OR, 1.17; 95% CI, 1.04 to 1.32). However, significant differences were observed only in specific subgroups: adolescents, participants with mild obesity, and those assessed using enzyme-linked immunosorbent assay or LC-MS/MS detection methods. CONCLUSION: These findings indicated that VD status was inversely associated with the risk of healthy obesity, irrespective of age and obesity grade. Inconsistencies may be influenced by VD detection methods and assessment criteria.