A recent study showed that an HFD stimulated FA β-oxidation by increasing CPT1B and CPT2 expressions, whereas metformin (a drug for the treatment of type 2 diabetes) significantly down-regulated the CPT1B and CPT2 expressions in BAT compared with HFD-fed mice, indicating that metformin might improve the energy metabolism of BAT and might reduce compensated energy expenditure [43]. The gene discussed is CPT1B; the disease is type 2 diabetes mellitus.