Zahra Hajhashemy - Students’ Research Committee, Isfahan University of Medical Sciences, Isfahan, IranDepartment of Community Nutrition, School of Nutrition and Food Science, Food Security Research Center, Isfahan University of Medical Sciences, Isfahan, Iran
Parvane Saneei - Department of Community Nutrition, School of Nutrition and Food Science, Food Security Research Center, Isfahan University of Medical Sciences, Isfahan, Iran

Sources of Support: The financial support for conception, design, data analysis and manuscript drafting comes from Food Security Research Center, Isfahan University of MedicalSciences, Isfahan, Iran. Disclosure Statement: None of the authors had any personal or financial conflicts of interest.Background and Objective: Although previous observational studies investigated the association between waist circumference (WC) values and serum vitamin D levels, findingswere inconsistent. A systematic review and meta-analysis was performed to evaluate the effect of abdominal obesity based on WC on vitamin D deficiency or insufficiency in adults.Materials and Methods: A systematic search up to September ۲۰۲۰ was conducted in electronic databases including MEDLINE (Pubmed), EMBASE, Web of science (ISI), Scopusand Google scholar, for observational studies that investigated the association between abdominal obesity (based on WC) or different categories of waist circumference as theexposure and serum ۲۵-hydroxy vitamin D levels as the outcome. Eighteen cross-sectional studies were included in the review. WC values in relation to combined serum vitamin D deficiency and insufficiency (<۳۰ ng/ml) or vitamin D deficiency (<۲۰ ng/ml) were evaluated.Results: Combining ۸ effect sizes from ۵ investigations including ۷۹۹۷ individuals illustrated that high level of waist circumference compared to low level was related to ۸۲% increased odds of combined serum vitamin D deficiency and insufficiency (<۳۰ ng/ml) (OR: ۱.۸۲; ۹۵%CI: ۱.۳۴, ۲.۴۹). Moreover, in studies which investigated both genders together, highest versus lowest level of waist circumference was associated with ۶۱% increased odds of serum vitamin D deficiency (<۲۰ng/ml) (OR: ۱.۶۱; ۹۵%CI:۱.۱۲, ۲.۳۱). The same results were obtained in almost all subgroups according to several covariates.Conclusion: This meta-analysis of cross-sectional studies confirmed that highest versus lowest waist circumference values was related to elevated risk of combined vitamin D deficiency and insufficiency in adults. More prospective studies are needed to confirm causality.

Waist circumference; Central adiposity; Abdominal obesity; Vitamin D deficiency; Vitamin D insufficiency; Systematic review; Meta-analysis