The increase of FGF21 in HFD‐fed WT mice could be a response to reduced FGF21 sensitivity.[34] Because bid deficiency conferred a relatively normal metabolic condition following HFD feeding, lower levels of FGF21 could be another manifestation of the resistance of bid−/− mice to diet‐induced hepatic steatosis. This evidence concerns the gene FGF21 and fatty liver disease.