Search Strategy

We searched PubMed, Scopus, EMBASE, ISI Web of Science, and Cochrane databases through October 2021 in the English language to find studies investigating the prevalence of vitamin D status in patients with severe obesity who were candidates for bariatric surgeries. The systematic literature search was based on the following strategy: controlled vocabulary (i.e., MeSH and EMTREE terms) and specific text words. For each database search, adapted combinations of terms and words were applied. For example, in the search on the PubMed database, the following search terms were used: (“vitamin D,” “25-hydroxy vitamin D,” “vitamin D deficiency,” 25(OH) D, “Vitamin D deficiency” OR “Deficiency, Vitamin D” OR “Deficiencies, Vitamin D” OR “Vitamin D Deficiencies”) AND (“morbid obesity” OR “severe obesity” OR “Morbid Obesities” OR “Obesities, Morbid” OR “Obesity, Severe” OR “Obesities, Severe” OR “Severe Obesities” OR “Severe Obesities”). Moreover, bibliographies of all prior reviews and primary studies identified by search strategy were scanned for additional relevant publications. The authors decided which trials to include (authors 1, 2, and 3) in a blinded manner, with discrepancies resolved via discussion.