CEACAM1 and obesity due to melanocortin 4 receptor deficiency: Increased lipolysis-driven hepatic fatty acid β-oxidation in humans with uncomplicated obesity (26) and its role in regulating hepatic de novo lipogenesis (27, 28) propose an important role for the loss of hepatic CEACAM1 in the regulation of lipid homeostasis in hepatocytes derived from obese humans.