Therefore, in the present study we sought: 1) to determine whether Caucasian children and adolescents with overweight/obesity and NAFLD exhibit signs of renal functional alteration, as assessed by estimated glomerular filtration rate (eGFR) as well as by urinary albumin excretion, compared to those with overweight/obesity but without NAFLD; and 2) to assess whether PNPLA3 rs738409, TM6SF2 rs58542926, GCKR rs1260326, and MBOAT7 rs641738 gene polymorphisms may influence renal function in overweight/obese youths with and without NAFLD. The gene discussed is GCKR; the disease is obesity due to melanocortin 4 receptor deficiency.