Metformin and Body Weight: A Narrative Review of Clinical Evidence and Mechanistic Insights

Background: Obesity, defined by pathological accumulation of adipose tissue increases the cardiovascular event and metabolic complication such as type 2 diabetes and dyslipidemia.  the World Health Organization (WHO) defines obesity as abnormal fat deposition impairing health, primarily driven by energy intake-expenditure imbalance. Weight remains a critical therapeutic target. Metformin, demonstrates promising weight-lowering properties in clinical studies. Aim: This narrative review examines metformin’s efficacy as a weight-loss intervention and its underlying biological mechanisms. Methods: this narrative review searches following electronic sites: PubMed, Scopus, Web of Science, and Science Direct for peer-reviewed studies on metformin and weight loss, these articles published between 2015-2025. Using key word (Obesity, weight loss, metformin, gut microbiome, AMPK, GLP-1, GDF15, Lac-phe), including original research article or high systematic reviews and meta-analysis to investigate effect of metformin on body weight or food intake. Excluding studies deal with coadministration metformin with other weight reduction strategy. also exclude case report with poor data and conference abstracts. Finally, 71 studies meet these criteria and consider basis for this review. Conclusion: The evidence strongly suggests that metformin encourages weight loss by acting in multiple ways, both systemically and locally (in the gut). Its key actions include activating the body's central energy sensor, AMPK, as well as promoting the gut's release of appetite-suppressing hormones (GLP-1, PYY). Furthermore, it influences other appetite-regulating metabolites (Lac-Phe, GDF15) and positively alters the gut's bacterial makeup. Together, these pathways reduce appetite and improve metabolic stability, making metformin a useful therapeutic choice for weight management, in addition to its well-known benefits for blood sugar.