For PPARδ, circadian rhythmicity was observed in athletes, obese and T2D using JTK-cycle (JTK_CYCLE p < 0.05), and one-way ANOVA analysis revealed significantly different gene expression levels of PPARδ between time points in athletes and obese, p < 0.001 and p < 0.009, respectively. This evidence concerns the gene PPARD and type 2 diabetes mellitus.