LEP and obesity due to melanocortin 4 receptor deficiency: In general, two types of obesity could be distinguished: (i) the genetic one [45], such as leptin deficiency [46], in which mutations can lead to the over-accumulation of fat or, in some cases, linked to pharmacological treatments such as anti-HIV therapies [47], and (ii) the obesity linked to the lack of control of appetite, as well as universal access to food regimens over-rich in both fat and sugar (commonly called cafeteria regimens [48] or Western diet [49]).