Obesity is a multifactorial, chronic disease that involves an abnormal or excessive accumulation of body fat that poses a serious risk to overall health.

Clinically, obesity is often assessed using the Body Mass Index (BMI), a simple screening tool calculated by dividing a person’s weight in kilograms by the square of their height in meters (kg/m²). According to the World Health Organization (WHO), a BMI of 30 or above is classified as obese. However, BMI alone does not account for fat distribution or muscle mass, and thus, other clinical assessments such as waist circumference, body composition analysis, and metabolic health markers are crucial for a more accurate diagnosis.

Obesity is not merely an aesthetic concern. It represents a complex medical condition with diverse underlying causes and substantial implications for long-term health. The pathophysiology of obesity involves an intricate interplay between genetic predisposition, metabolic dysfunction, and environmental influences that disrupt the body’s energy balance and regulatory mechanisms.

The development of obesity is driven by a chronic imbalance between caloric intake and energy expenditure.

However, this oversimplifies a condition influenced by a vast array of biological, behavioral, and environmental factors. Genetics play a significant role in determining an individual’s susceptibility to obesity, with studies identifying hundreds of genes associated with weight regulation, fat storage, and energy metabolism. Hormonal regulation, particularly the role of hormones like leptin, ghrelin, and insulin, also contributes to dysregulated appetite control and energy use, exacerbating weight gain.

Beyond genetic predisposition, lifestyle factors are critical in the development of obesity. Diets rich in calorie-dense, highly processed foods combined with a sedentary lifestyle are major contributors. However, environmental and socioeconomic factors also heavily influence these lifestyle choices. Urbanization, limited access to healthy foods, socioeconomic disparities, and cultural norms often create environments where healthier choices are less accessible or more expensive, perpetuating the obesity epidemic.

In addition, psychological factors such as stress, depression, and emotional eating are significant contributors to weight gain. Certain medical conditions, including hypothyroidism, polycystic ovary syndrome (PCOS), and Cushing's syndrome, along with medications like corticosteroids and antidepressants, can also predispose individuals to weight gain or make weight loss more challenging.