FGF21 and metabolic disease: Previous studies have highlighted FGF21’s roles in promoting hepatic ketogenesis and adipose tissue lipolysis during fasting and reducing plasma glucose, FFAs and TG in metabolic diseases.5,6,9,30,70 Unlike BAT, an energy consumer that benefits from FGF21’s action on mobilizing ketones and FFAs during cold exposure, the liver and WAT do not utilize these products themselves.