Analysing by manifestations, lower levels of baseline activated T CD4+ lymphocytes (CD69) were observed in patients with obesity (1 ± 0.2 vs. 2.4 ± 0.7%; p = 0.076) and metabolic syndrome (1 ± 0.2 vs. 2.2 ± 0.5%; p = 0.039). This evidence concerns the gene CD69 and obesity due to melanocortin 4 receptor deficiency.