This article gives an overview, citing animal and clinical studies, of the effects of increased intra-abdominal pressure (IAP) in severe obesity. Animal studies demonstrate that increased IAP increases pleural pressure, cardiac filling pressures, femoral venous pressure, renal venous pressure, systemic blood pressure, and vascular resistance, renin and aldosterone levels, and intracranial pressure. Thus, the comorbidities presumed secondary to increased IAP in obese patients include congestive heart failure, hypoventilation, venous stasis ulcers, gastroesophageal reflux, urinary stress incontinence, incisional hernia, pseudotumor cerebri, proteinuria, and systemic hypertension.