Metabolic syndrome prevalence in the Iranian adult's general population and its trend: A systematic review and meta-analysis of observational studies.

•We assessed 15-year trend of metabolic syndrome (MetS) by gender and international definition in Iran—ATPIII and IDF criteria.•Comparing the agreement between pooled estimates in NCEP ATPIII and IDF metabolic syndrome definitions by gender.•Pooling the summary measure of enough studies on general population.•During 15-year period (2000–2015) prevalence of MetS in both males and females showed decreasing trend.