Insomnia is a highly prevalent sleep disorder worldwide, with an increasing incidence in athletes, older adults, university students, and individuals with metabolic syndrome. This disorder has been associated with metabolic dysfunction, cardiovascular diseases, and genetic instability. Recent evidence suggests that insomnia negatively impacts cardiorespiratory fitness, insulin sensitivity, and overall health through mechanisms involving neuroendocrine dysregulation, oxidative stress, and alterations in energy metabolism. However, the specific biological and environmental factors that contribute to its prevalence and health consequences remain poorly understood, particularly across different populations. Understanding these associations is crucial for developing effective prevention and intervention strategies to mitigate the long-term impact of insomnia. Therefore, this study aims to analyze the impact of insomnia on body composition, cardiorespiratory fitness, metabolic flexibility, and DNA integrity, across populations with high prevalence of insomnia, including athletes, older adults, university students, and individuals with metabolic syndrome. This study will also investigate which biological and lifestyle behaviors contribute to insomnia and its health consequences. By doing so, this work will provide critical insights into the physiological and molecular mechanisms that link insomnia with metabolic and cardiovascular dysfunction, contributing to the development of targeted interventions for at-risk populations