Notably, there were no significant differences, either pre- or post-puberty, in leptin levels between the two groups of patients with overweightness/obesity (ASD+/Ob+ and ASD−/Ob+) or between the two groups with normal body weight (ASD+/Ob− and ASD−/Ob−) (Figure 2 and Figure 3), although the comparison of non-ASD and ASD lean pre-pubertal children revealed a distinct trend toward significance (p = 0.15, higher leptin levels in the ASD+/Ob− group than in the ASD−/Ob− group) (Figure 2). This evidence concerns the gene LEP and obesity due to melanocortin 4 receptor deficiency.