Plasma IL-17 levels were higher in 42 volunteers with a BMI >35 compared to those of 34 volunteers with normal BMIs. IL-17 levels were significantly higher in men with a BMI >35 than women with a BMI >35. IL-17 was elevated in those with a BMI >35 that had type 2 diabetes versus those without type 2 diabetes. Here, IL17A is linked to type 2 diabetes mellitus.