Obesity is currently recognised as a chronic disease that is often relapsing and progressive. This requires attention for long-term monitoring to treat or prevent obesity-related complications. This article discusses the biology of weight regulation as a basis for understanding obesity as a disease, and to appreciate the complex and multifactorial pathogenesis of obesity. With this understanding of the factors involved in perpetuating obesity in different individuals, the approach to patients with obesity should be as comprehensive and systematic as with other chronic diseases. Management strategies and treatment plans, which need to have long-term weight maintenance and weight regain prevention in mind, can be more individualised for patients with obesity.