IGF1 and obesity due to melanocortin 4 receptor deficiency: Carcinogenic mechanism of obesity could stem from insulin resistance, which increases chronic inflammation, oxidative stress, DNA damage, and insulin-like growth factor-1 (IGF-1) levels, further stimulating cell proliferation [55]. Obese individuals with type 2 diabetes mellitus has increased risk of developing colon cancer, which is thought due to prolonged exposure to high levels of insulin in the colon [56].