Tryptophan (Trp), an essential amino acid, plays a central role in metabolism, inflammation, immunity, and energy homeostasis. It is primarily metabolized through the kynurenine, indole, and serotonin pathways, generating metabolites with either protective or harmful effects depending on the physiological and tissue context. Dysregulation of these pathways contributes to obesity, diabetes, and cardiovascular diseases. Understanding these mechanisms paves the way for personalized nutritional and therapeutic strategies to prevent and manage cardiometabolic diseases.