Overnutrition is the state resulting from the chronic consumption of nutrients, particularly energy, in excess of physiological requirements, leading to a sustained positive energy balance. As a research concept, it investigates the multifactorial etiology, biological mechanisms, physiological consequences, and associated pathologies arising from this condition, including metabolic dysregulation, excessive adipose tissue accumulation, and the development of related chronic diseases. This field is significant for understanding the complex interplay of genetic, environmental, and behavioral factors driving nutrient excess and for informing public health strategies and clinical interventions aimed at prevention and management.