Although Tph1-deficient mice fed a normal diet have no significant effect on body weight, Tph1-deficient mice fed a high-fat diet are protected from obesity and insulin resistance by promoting brown adipose tissue-mediated thermogenesis . On the other hand, Tph2-deficient mice fed a normal diet decrease food intake and body weight . Because PCPA inhibits Tph1 and Tph2, both mechanisms could contribute to weight loss.