As Schreiber et al. [118] conclude, “Interdependence of lipid catabolism and synthesis provides a rational explanation for the lack of obesity in ATGL-deficient mice and humans.” Whereas alleles of the FTO gene are associated with appetite or food intake, this observation provides no information regarding metabolic pathways or causal direction. This evidence concerns the gene PNPLA2 and obesity due to melanocortin 4 receptor deficiency.