LEP and obesity due to melanocortin 4 receptor deficiency: Indeed, the modern human diet is rich in saturated fat, especially in Western countries, and mice fed an HFD for a prolonged period develop an obesity syndrome showing all the hallmarks of human obesity, such as leptin resistance, impaired glucose tolerance, dyslipidaemia, hypertension, hepatic steatosis and adipose tissue inflammation (Panchal and Brown, 2011; Giordano et al., 2013).