Osteoporosis, obesity, and diabetes are the most commonpathologies seen in highly industrialized countries and the costimpact to treat these diseases is enormous and still growing.Since PPAR-γ is positioned at the cross-roads of thecontrol of bone mass, energy expenditure, and glucose metabolism,changes in its activity, which occur either naturally during agingor during antidiabetic therapy using TZDs, may result in unwantedeffects on the skeleton. The gene discussed is PPARG; the disease is obesity due to melanocortin 4 receptor deficiency.