Irisin in Pediatric Obesity: A Narrative Review of Current Evidence.

Obesity in children and adolescents represents an escalating global health challenge associated with chronic low-grade inflammation and dysregulation of myokine and adipokine secretion. Irisin, encoded by the FNDC5 gene, plays a pivotal role in energy homeostasis by promoting the "browning" of white adipose tissue (WAT) and increasing energy expenditure through thermogenesis. The aim of this study was to establish the diagnostic and therapeutic significance of irisin in the context of childhood obesity and to assess its usefulness as a marker for the early detection and monitoring of metabolic disorders. A comprehensive literature search was conducted using the PubMed database. Findings were limited to studies published within the last five years, from April 14, 2021, to April 14, 2026. Only studies in English were included. We used the following keywords and phrases: irisin; FNDC5; obesity; child; children; pediatric; adolescence; adolescent. Twenty studies met the inclusion criteria and were included in this narrative review. Studies confirmed that serum irisin concentration typically correlates positively with BMI and leptin levels, which may be described as a compensatory mechanism for improving insulin sensitivity. In obese adolescent girls with polycystic ovary syndrome (PCOS), irisin levels are lower but increase with a reduction in fat mass. High-intensity interval training (HIIT) stimulates higher irisin release than moderate-intensity training. In rarer conditions, such as Prader-Willi syndrome (PWS), irisin levels are reduced, which is associated with impaired bone metabolism and decreased muscle mass. Irisin can also act as a marker of hepatic steatosis and as a factor supporting executive functions in overweight children. Irisin represents a promising and sensitive biomarker of metabolic status and adipose tissue content in pediatric patients. Its monitoring may allow for a clear assessment of therapeutic effectiveness and dynamic changes in the child's metabolic profile.