Obesity has reached epidemic proportions in many countries and is an established risk factor in many chronic illnesses, but its role in acute illness is less clear. Pancreatologists have long recognized obesity as a risk factor for a poor outcome in severe acute pancreatitis. There are now several studies that have identified obesity as a primary risk factor for developing local complications (abscess, pseudocyst, necrosis), organ failure, and death. Indeed, meta-analysis of these studies gives a relative risk of 4.3 for local complications, 2.0 for systemic complications, and 2.1 for death. This has led to proposed modifications of acute pancreatitis scoring systems to include obesity as an independent primary predictive factor of severe disease. Obesity is associated with a low-grade inflammatory state, which may predispose obese patients to such complications. Furthermore, visceral obesity and visceral adipose tissue may be particularly important in underlying the pathophysiology of these observations.