Gut hormones like GLP‑1, GIP, and glucagon control hunger and can affect metabolism beyond just eating. A new drug called retatrutide, which activates all three hormone receptors at once, has been shown in recent human studies to help people lose weight and improve metabolic health. However, the exact dosing, long‑term safety, and how diet, exercise, and sleep interact with these hormones still need more research.

Various gut hormones interact with the brain through delicate communication, thereby influencing appetite and subsequent changes in body weight. This review summarizes the effects of gut hormones on appetite, with a focus on recent research. Ghrelin is known as an orexigenic hormone, whereas glucagon-like peptide-1 (GLP-1), glucose-dependent insulinotropic polypeptide (GIP), cholecystokinin (CCK), postprandial peptide YY (PYY), and oxyntomodulin (OXM) are known as anorexigenic hormones. Recent human studies have revealed that gut hormones act differently in various systems, including adipose tissue, beyond appetite and energy intake, and even involve in high-order thinking. Environmental factors including meal schedule, food contents and quality, type of exercise, and sleep deprivation also play a role in the influence of gut hormone on appetite, weight change, and obesity. Recently published studies have shown that retatrutide, a triple-agonist of GLP-1, GIP, and glucagon receptor, and orforglipron, a GLP-1 receptor partial agonist, are effective in weight loss and improving various metabolic parameters associated with obesity. Various gut hormones influence appetite, and several drugs targeting these receptors have been reported to exert positive effects on weight loss in humans. Given that diverse dietary and environmental factors affect the actions of gut hormones and appetite, there is a need for integrated and largescale long-term studies in this field.