Nonalcoholic steatohepatitis (NASH) is asymptomatic, but associated with obesity and the metabolic syndrome in most patients. Clinical scoring systems may guide the decision to perform a liver biopsy in the morbidly obese. Bariatric surgery is an effective treatment option for severely obese patients (BMI ≥ 35 kg/m), and provides for long-term weight loss and resolution of obesity-associated diseases in most patients. Although no prospective randomized trials are available and outcomes after long-term follow-up are still under scrutiny, regression and/or histologic improvement of NASH have been documented after weight loss after bariatric surgery using current techniques. Rare cases of fulminant steatohepatitis during the first postoperative year in patients with excessive rates of weight loss have been reported and fibrotic changes may progress. Identifying the factors associated with such outcomes and the independent roles of weight loss and other metabolic changes after bariatric surgery on improvements in obesity-associated diseases could potentially lead to a tailored and personalized approach to obesity and its consequences.