Obesity is associated with increased severity of acute pancreatitis (AP). We recently developed a model of AP induced by administration of interleukin (IL)-12+IL-18, two cytokines that are elevated in patients with AP. In this model, severe AP develops in obese leptin-deficient ob/ob mice compared to lean littermates. In the present report, we evaluated the pancreatic response of diet-induced obesity (DIO) mice to IL-12+IL-18. Body weight loss and adipose tissue necrosis were more severe and prolonged in cytokine-injected DIO compared to lean mice. Edematous AP developed in lean mice, whereas DIO mice developed necrotizing AP. Obese DIO mice developed more severe hypocalcemia, increased liver damage and a heightened acute-phase response compared to lean mice, although leukopenia and thrombocytopenia were of comparable severity in lean and DIO mice. Serum levels of IL-6, IL-10, and IL-22 were significantly higher in DIO compared to lean mice, whereas interferon-gamma and tumor necrosis factor-alpha did not differ between the two groups. In conclusion, obesity induced by high-fat diet is associated with increased disease severity and duration in the model of AP induced by administration of IL-12+IL-18.