Obesity

Obesity is a chronic, multifactorial disease characterized by an excessive accumulation of body fat that impairs health. According to the criteria established by the World Health Organization (WHO), obesity is defined as a Body Mass Index (BMI) of 30 kg/m² or greater. As a complex chronic disease, obesity generally requires a comprehensive, multidisciplinary treatment approach that combines nutritional therapy, increased physical activity, behavioral interventions, psychological support, and, where appropriate, pharmacological treatment or bariatric surgery.

Contrary to the common misconception that obesity is merely the result of overeating, it is a highly complex medical condition influenced by the interaction of biological, behavioral, environmental, and social factors. The principal contributors include:

• Energy Balance: A sustained positive energy balance—where energy intake consistently exceeds energy expenditure—results in the storage of excess energy as body fat.
• Genetic and Biological Factors: Genetic predisposition, individual metabolic characteristics, hormonal regulation, and neuroendocrine mechanisms significantly influence body weight and fat distribution.
• Environmental and Lifestyle Factors: Sedentary behavior, widespread availability of energy-dense, highly processed foods, poor dietary habits, urbanization, and socioeconomic conditions contribute substantially to obesity risk.
• Medical Conditions and Medications: Certain endocrine disorders, chronic diseases, and medications—including corticosteroids, some antidepressants, antipsychotics, and antidiabetic agents—may promote weight gain or make weight management more difficult.

Although obesity has multiple contributing factors, the principle of energy balance remains fundamental. Body weight changes are ultimately determined by the relationship between energy intake and energy expenditure. When caloric intake exceeds total energy expenditure over an extended period, excess energy is stored primarily as adipose tissue, resulting in weight gain. Conversely, when energy expenditure consistently exceeds caloric intake—whether through increased physical activity, dietary restriction, or certain disease states—the body mobilizes stored energy reserves, leading to weight loss. This relationship is governed by the fundamental laws of energy conservation. However, biological adaptations such as hormonal regulation, metabolic adaptation, appetite control, and changes in resting energy expenditure can significantly influence both sides of the energy balance equation, making long-term weight management considerably more complex than a simple matter of willpower.

Obesity places substantial physiological stress on virtually every organ system and is recognized as one of the leading risk factors for numerous chronic diseases, including:

• Type 2 diabetes mellitus
• Arterial hypertension
• Cardiovascular diseases, including coronary artery disease and stroke
• Obstructive sleep apnea
• Osteoarthritis and other musculoskeletal disorders
• Non-alcoholic fatty liver disease (NAFLD)
• Several types of cancer, including colorectal, breast (postmenopausal), endometrial, kidney, and esophageal cancer
• Chronic kidney disease
• Mental health disorders such as depression and anxiety
• Reduced quality of life and premature mortality

Today, obesity represents one of the most significant public health challenges worldwide. The global prevalence of obesity has increased dramatically over recent decades across both developed and developing countries. This continuing trend is accompanied by a substantial rise in obesity-related chronic diseases, increasing healthcare expenditures, reduced workforce productivity, and growing socioeconomic burdens. Without effective prevention and treatment strategies, these trends are expected to place considerable strain on healthcare systems and social security systems worldwide.

Recognizing obesity as a chronic disease rather than solely a lifestyle issue is essential for developing effective prevention strategies, improving access to evidence-based treatment, and reducing its long-term health, social, and economic consequences. Addressing the obesity epidemic through coordinated public health policies, education, early intervention, and multidisciplinary clinical care represents one of the most important societal challenges of the 21st century.