AIM: To evaluate the relationship between leptin and systemic inflammation in acute pancreatitis. METHODS: Consecutive patients with acute pancreatitis were included. Body mass index and serum samples were obtained at admission. Leptin, TNF-α, IL-6, -8 and -10 levels were determined by ELISA. Severity was defined according to Atlanta criteria. RESULTS: Fifty-two (29 females) patients were studied. Overall body mass index was similar between mild and severe cases, although women with severe pancreatitis had lower body mass index (P = 0.04) and men showed higher body mass index (P = 0.05). No difference was found in leptin levels regarding the severity of pancreatitis, but higher levels tended to appear in male patients with increased body mass index and severe pancreatitis (P = 0.1). A multivariate analysis showed no association between leptin levels and severity. The strongest cytokine associated with severity was IL-6. Correlations of leptin with another cytokines only showed a trend for IL-8 (P = 0.058). CONCLUSION: High body mass index was associated with severity only in males, which may be related to android fat distribution. Serum leptin seems not to play a role on the systemic inflammatory response in acute pancreatitis and its association with severe outcome in males might represent a marker of increased adiposity. METHODS: Consecutive patients with acute pancreatitis were included. Body mass index and serum samples were obtained at admission. Leptin, TNF-α, IL-6, -8 and - Overall levels of mass were similar between mild and severe cases, although women with severe pancreatitis had lower body mass index (P = 0.04) and men showed higher body mass index (P = 0.05). No difference was found in leptin levels regarding the severity of pancreatitis, but higher levels tended to appear in male patients with increased body mass index and severe pancreatitis (P = 0.1). A multivariate analysis showed no association between leptin levels and severity. The strongest cytokine associated with severity was IL-6. Correlations of leptin with another cytokines only showed a trend for IL-8 (P = 0.058). CONCLUSION: High body mass index was associated with severity only in males, which may be related to android fat distribution. Serum leptin seems not to play a role on the systemic inflammatory response in acute pancreatitis and its association with severe outcome in males might represent a marker of increased adiposity.