LEP and obesity due to melanocortin 4 receptor deficiency: In this study, we first aim to determine the prevalence of known disease-causing variants and rare variants of unknown clinical significance with a potential to adversely affect gene function in the leptin-melanocortin pathway in a large cohort of obese children, to assess the feasibility of genetic screening for monogenic obesity and to have the possibility to intervene early to more effectively prevent the development of obesity.