This review is based on a search in biomedical databases (PubMed, Quertle) for the terms “obese, insulin resistant, type 2 diabetes, ROS, human, oxidative stress” as well as “obese, insulin resistant, type 2 diabetes, acute, chronic, exercise, ROS, human, oxidative stress” and mainly focuses on studies published during the last 5 years but also addresses relevant older studies. This evidence concerns the gene INS and type 2 diabetes mellitus.