We found that objectively measured moderate–vigorous PA was independently and inversely correlated with the expression of p16INK4a and p21Cip1 in the peripheral blood mononuclear cell (PBMCs) of adults with obesity; however, chronological age, body mass index, body fat, maximal oxygen consumption, light PA, sedentary behaviors, and sleep duration were not. The gene discussed is CDKN1A; the disease is obesity due to melanocortin 4 receptor deficiency.