FOXO1 and Obesity: Because HFD activates Foxo1 in CD4+ T cells in adipose tissues, activation of Foxo1 in CD4+ T cells under HFD may suppress gene expression of Gata3 and Ccr4, resulting in a decrease of homing of Th2 cells into adipose tissues, inhibition of brown and beige adipocytes, and decreased energy expenditure, finally leading to a vicious cycle of obesity.