Obesity is a chronic, multifactorial, heterogeneous disease defined as the “amount of excess body fat at which health risks to individuals begin to increase.” Obesity is usually classified by body mass index. Obesity prevalence in the United States is 39.6% and is projected to increase to 50% by 2030 (Figure 65.1). Obesity is associated with a higher risk for mortality (Figure 65.2). Multiple etiological factors have been associated with obesity which can be classified as individual and environmental (Figure 65.3). The regulation of energy balance is tightly regulated by the brain–gut–liver–adipose tissue axis (Figure 65.4). Obesity is a major risk factor for gastrointestinal and liver disease (Figures 65.5 and 65.6).

The treatment of obesity is a continuum of care with four main phases: (1) obesity assessment, (2) intense weight loss, (3) weight loss maintenance, and (4) prevention of weight regain (Figure 65.7). The cornerstone of weight loss is lifestyle modifications (dietary and behavioral interventions in addition to physical activity). When these fail, second‐level tools should be considered (pharmacotherapy, bariatric endoscopy, and surgery). Endoscopic bariatric therapies (EBT) are minimally invasive procedures for weight loss (Figure 65.8). Gastroenterologists are often confronted with complications indirectly related to the surgery, such as anastomotic ulceration, band erosion, stricture, and fistulas, which may require endoscopic therapy (Figures 65.9–65.12).