Genes involved in type 1 diabetes mellitus, such as human leukocyte antigen (HLA)-DQA1, HLA-DQB1 were hypermethylated in the promoter region of whole blood sample from offspring born after maternal bariatric surgery compared to before bariatric surgery, and genes involved in type 2 diabetes mellitus includes POMC, IGF2, insulin receptor (INSR), fat mass- and obesity-associated protein (FTO) as well as tumor necrosis factor (TNF), were either hypermethylated (POMC, IGF2, and INSR) or hypomethylated (FTO and TNF) [76,77]. This evidence concerns the gene FTO and type 2 diabetes mellitus.