TGR5, the G-protein-coupled bile acid receptor, controls the metabolism of cholesterol, bile acids, fats, and carbohydrates, as well as insulin and systemic energy expenditure, and has been shown to boost metabolic rate, uptake of oxygen, and decrease obesity and hepatic steatosis in a mouse model of obesity [83–85]. The gene discussed is INS; the disease is obesity due to melanocortin 4 receptor deficiency.