Although the precise mechanism of how obesity increases the risk of kidney cancer has not been identified, the following hypothesis may explain the link.21,22 Obesity is associated with hyperinsulinemia; insulin stimulates cell growth either directly through the insulin receptor, or through its ability to interact with the insulin-like growth factor-1 (IGF-1) receptor. Here, IGF1 is linked to obesity due to melanocortin 4 receptor deficiency.