Nygaard EB, et al. - In the present study, researchers measured in obese and lean subjects the impact of 60 hours of fasting on plasma fibroblast growth factor 21 (FGF21) levels, and identified the gene expression of Beta-klotho (KLB) and FGFR1c in subcutaneous white adipose tissues (WAT) before, during, and following 60 hours of fasting. For this investigation, eight obese (BMI > 30 kg/m²) and seven lean subjects (BMI < 25 kg/m²) fasted for 60 hours, with blood samples taken at 0 hours and after 12, 36 and 60 hours of fasting. In obese subjects, plasma FGF21 was significantly reduced after fasting. On the other hand, no change in plasma FGF21 was seen in lean subjects. Findings revealed that KLB was significantly reduced in WAT after fasting in both lean and obese subjects, showing a possible important adaptive regulation of KLB in response to fasting.