In the current study, we defined lean and obese T2D using BMI cut-off values determined to be optimal for the Chinese Han population.[16,17] Our study identified SNPs in or near CDKAL1, CDKN2BAS, and KCNQ1 as significantly related to the risk for lean T2D with effective sizes ranging from 1.20 to 1.28, values which were obviously higher than the effective size for obese T2D (ORs 1.01–1.15). This evidence concerns the gene KCNQ1 and type 2 diabetes mellitus.