Core Viewpoint - The article discusses the potential of Fibroblast Growth Factor 21 (FGF21) as a therapeutic agent to improve metabolism and promote longevity, particularly in the context of obesity and aging-related metabolic issues [2][5]. Group 1: FGF21 and Aging - Approximately 35% of adults aged 65 and older in the U.S. are classified as obese, highlighting the need for therapies targeting age-related metabolic issues [2][5]. - FGF21 is primarily produced by the liver and acts as an endocrine hormone, responding to various cellular stressors, showing promise in treating metabolic diseases such as type 2 diabetes and non-alcoholic fatty liver disease [5][6]. Group 2: Research Findings - The study published in Cell Metabolism indicates that FGF21 promotes longevity in diet-induced obese mice through metabolic benefits independent of growth suppression [3][8]. - Overexpression of FGF21 in adult mice led to increased lifespan, improved insulin sensitivity, reduced liver fat degeneration, and lower levels of inflammatory immune cells in visceral fat tissue, even without the presence of adiponectin [6][8]. Group 3: Mechanisms of Action - FGF21 overexpression increases energy expenditure in high-fat diet-fed mice without affecting cold tolerance [8]. - The beneficial effects of FGF21 are primarily mediated through adipose tissue, suggesting its potential in treating metabolic syndrome and age-related diseases by promoting healthier metabolic states under dietary stress [9].