The present study is retrospective design and the study subjects were volunteers in a healthy screening program, which may have created a selection bias (e.g., there is possibility that overweight subjects may have moved from health screening to the treatment of obesity-related diseases and thus the effects of PNPLA3 genotype might have only been observed among normal weight subjects). This evidence concerns the gene PNPLA3 and obesity due to melanocortin 4 receptor deficiency.