In an obesity animal model induced by a hypercaloric diet, retroperitoneal AT from pregnant rat showed at the mid-gestation lower levels of Per1 and Rev-erbα expression, in late pregnancy a reduction of Bmal1 and Cry1 and throughout the gestation period, it was observed a down-regulation of the gene Per2 (Figure 1) [46,47]. This evidence concerns the gene PER2 and Obesity.