Hyperinsulinemia, which occurs as a consequence of lipid-induced insulin resistance and may also hasten its progression, is one of many putative links that may explain the association between obesity and cancer: insulin promotes tumor cell division in vitro [6–10], and plasma insulin concentrations are independently correlated with an increased risk and accelerated progression of both breast [11–15] and colon cancer [16–20]. This evidence concerns the gene INS and obesity due to melanocortin 4 receptor deficiency.