UCP2 KO mice were protected from high fat diet (HFD)-induced obesity. (A) 6-week-old C57BL6 mice were fed an HFD for 16 weeks, adipocytes and SVF from eWAT were isolated, and Ucp2 mRNA expression was analyzed (n = 5 for NCD and n = 11 for HFD). 3T3L1 cells were differentiated and the mRNA expression levels of the (B) differentiation marker Pparγ and (C) Ucp2 were detected. (D) Photographs of WT and KO mice after 2 weeks of NCD and HFD. (E) Body weight graph of 6-18-week-old mice in each group. (F) Graph of body weight gain throughout the experiment. (G) Body composition data. (H) Photographs of WAT of HFD-induced WT and KO mice. (I) WAT weight graph. (J) H&E staining of epididymal adipose tissue. (K) Adipocyte sizes were quantified. Data are presented as the mean ± SEM. *P < 0.05, **P < 0.01, ***P < 0.001.