On the other hand, although plasma leptin level was elevated in the obesity-prone FX subgroup in comparison to the obesity-prone CS subgroup, the obesity-prone FX subgroup did not have significant increase in fat mass; yet, the fat mass was significantly lower in the obesity-prone CS subgroup in comparison to the obesity-prone NR subgroup. The gene discussed is LEP; the disease is obesity due to melanocortin 4 receptor deficiency.