Still, sound evidence of direct effects in humans remains to be determined; it is unclear whether environmental obesogens, singly or in combination, act through known metabolic and/or adipogenic mechanisms (e.g., via PPARγ) to cause clinically significant outcomes in humans, such as obesity, type 2 diabetes, insulin resistance syndrome, and polycystic ovary syndrome. This evidence concerns the gene PPARG and polycystic ovary syndrome.