The molecular analyses conducted by Joosen et al. [50] revealed that changes in the expression levels of peroxisome proliferator-activated receptor γ1 and 2, and the aP2 transcriptional factor, were positively related to changes in plasma leptin in women without obesity who received a 50% increase in energy intake for two weeks. The gene discussed is LEP; the disease is obesity due to melanocortin 4 receptor deficiency.