In addition to the mechanical effects of obesity, such as an increase in intra-abdominal pressure caused by excess adipose tissue, adipose tissue secretes various adipokines, such as tumor necrosis factor (TNF), IL-6, leptin, and insulin-like growth factor-1 (IGF-1), which are considered to have pathogenic effects in relation to gastrointestinal cancer. The gene discussed is IGF1; the disease is obesity due to melanocortin 4 receptor deficiency.