Metabolic syndrome (MetS) is a complex disorder characterized by a cluster of interconnected factors that increase the risk of cardiovascular diseases and type 2 diabetes. Multiple definitions of MetS exist, leading to confusion about whether they identify the same individuals or represent risk factors. Recent research has identified additional factors linked to MetS, highlighting the need for uniform criteria to define it for better comparisons and risk identification. MetS is increasingly prevalent in children and adolescents, prompting a focus on established risk factors rather than MetS diagnosis in this age group. MetS is defined by components such as dyslipidemia, elevated blood pressure, and dysregulated glucose homeostasis, with abdominal obesity and insulin resistance as key features. Other factors like chronic inflammation, fatty liver disease, and sleep apnea have also been added to the definition, complicating it further. Despite various definitions, there is no universally accepted pathogenic mechanism or diagnostic criteria. The WHO, NCEP:ATPIII, and IDF have proposed different definitions, with the IDF focusing on abdominal obesity and the NCEP:ATPIII emphasizing waist circumference. However, these definitions vary in their applicability across ethnic groups, particularly in identifying obesity cut-offs. The prevalence of MetS varies depending on the criteria used and the population studied. It is high and rising in Western societies, largely due to the obesity epidemic. The IDF and NCEP:ATPIII definitions show similar prevalence rates, but the IDF uses lower waist circumference cut-offs, leading to higher prevalence estimates. MetS is associated with increased risks of cardiovascular disease, stroke, and type 2 diabetes. However, some studies have not found a significant association between MetS and cardiovascular risk, suggesting the need for further research. MetS is influenced by genetic and environmental factors, with obesity and insulin resistance at its core. Other factors such as chronic stress, dysregulation of the HPA axis, and oxidative stress also contribute to its pathogenesis. Adipose tissue produces bioactive substances that induce insulin resistance and contribute to metabolic abnormalities. The role of microRNAs and other factors in MetS is also being explored. In children and adolescents, MetS definitions are not yet fully validated, and the diagnosis may not be reliable. The prevalence of MetS in children is increasing, highlighting the need for a focus on established risk factors rather than MetS diagnosis. The IDF has proposed age-specific definitions for children, but there is still a lack of consensus on the best approach for diagnosing and managing MetS in this population. In conclusion, the need for a unified definition of MetS remains, as it is crucial for accurate risk identification and management. While the IDF and AHA/NHLBI definitions are currently widely used, further research is needed to refine the criteria and improve the understanding of MetS. The focus should be on established risk factors, particularly in children and adolescents, to better address the growing prevalence of MetS.Metabolic syndrome (MetS) is a complex disorder characterized by a cluster of interconnected factors that increase the risk of cardiovascular diseases and type 2 diabetes. Multiple definitions of MetS exist, leading to confusion about whether they identify the same individuals or represent risk factors. Recent research has identified additional factors linked to MetS, highlighting the need for uniform criteria to define it for better comparisons and risk identification. MetS is increasingly prevalent in children and adolescents, prompting a focus on established risk factors rather than MetS diagnosis in this age group. MetS is defined by components such as dyslipidemia, elevated blood pressure, and dysregulated glucose homeostasis, with abdominal obesity and insulin resistance as key features. Other factors like chronic inflammation, fatty liver disease, and sleep apnea have also been added to the definition, complicating it further. Despite various definitions, there is no universally accepted pathogenic mechanism or diagnostic criteria. The WHO, NCEP:ATPIII, and IDF have proposed different definitions, with the IDF focusing on abdominal obesity and the NCEP:ATPIII emphasizing waist circumference. However, these definitions vary in their applicability across ethnic groups, particularly in identifying obesity cut-offs. The prevalence of MetS varies depending on the criteria used and the population studied. It is high and rising in Western societies, largely due to the obesity epidemic. The IDF and NCEP:ATPIII definitions show similar prevalence rates, but the IDF uses lower waist circumference cut-offs, leading to higher prevalence estimates. MetS is associated with increased risks of cardiovascular disease, stroke, and type 2 diabetes. However, some studies have not found a significant association between MetS and cardiovascular risk, suggesting the need for further research. MetS is influenced by genetic and environmental factors, with obesity and insulin resistance at its core. Other factors such as chronic stress, dysregulation of the HPA axis, and oxidative stress also contribute to its pathogenesis. Adipose tissue produces bioactive substances that induce insulin resistance and contribute to metabolic abnormalities. The role of microRNAs and other factors in MetS is also being explored. In children and adolescents, MetS definitions are not yet fully validated, and the diagnosis may not be reliable. The prevalence of MetS in children is increasing, highlighting the need for a focus on established risk factors rather than MetS diagnosis. The IDF has proposed age-specific definitions for children, but there is still a lack of consensus on the best approach for diagnosing and managing MetS in this population. In conclusion, the need for a unified definition of MetS remains, as it is crucial for accurate risk identification and management. While the IDF and AHA/NHLBI definitions are currently widely used, further research is needed to refine the criteria and improve the understanding of MetS. The focus should be on established risk factors, particularly in children and adolescents, to better address the growing prevalence of MetS.