Each year more than 150,000 Americans undergo bariatric surgery. Their main intent — to lose weight, which drastically improves obesity-related diseases, such as sleep apnea and hypertension and often puts diabetes into remission.

But our team at Tampa General Hospital and USF Health Bariatric Center has now identified another substantial benefit of bariatric surgery — reducing liver damage caused by nonalcoholic fatty liver disease (NAFLD) in severely obese patients. These findings  were presented at Digestive Disease Week® 2014 in Chicago, the world’s largest gathering of physicians and researchers in the fields of gastroenterology, hepatology, endoscopy and gastrointestinal surgery.

Our findings are significant for two reasons.

First, the prevailing teaching is that liver scarring and fibrosis are irreversible. Our study contradicts this convention, at least when it comes to early-stage fibrosis, and has the potential to change current clinical practice.

Second, and more importantly, we may be able to address a potential epidemic of NAFLD, because the disease is closely linked to obesity. In 2010, the CDC reported that more than 35 percent of U.S. adults were obese. Worldwide, according to the World Health Organization, 1.4 billion adults were overweight in 2008, and among them, the obese population nearly doubled since 1980 to reach 500 million. In addition to obesity, NAFLD is associated with other chronic diseases — diabetes, high blood pressure and high cholesterol — which are also gaining in prevalence globally. NAFLD can progress to liver cirrhosis and liver failure and currently is the second leading cause of liver transplantation.

Our team discovered this benefit of bariatric surgery when we compared liver biopsies from 152 patients — the first biopsy was done at the time of the bariatric procedure and the follow up biopsy was done an average of 29 months afterwards. We found that fat deposits on the liver resolved in 70 percent of patients. We also saw that reducing fat deposits resulted in improvement of liver inflammation, with lobular inflammation resolved in 74 percent of patients and steatohepatitis resolved in 88 percent of patients.

In addition, 32 of the 52 patients with stage two liver fibrosis experienced either improvement or resolution of their fibrosis. For 15 patients, fibrosis did not worsen. And, one of the three patients with cirrhosis of the liver showed improvement.

Currently, medical treatment of NAFLD is largely ineffective. As we continue to tackle the challenge of treating obese patients with nonalcoholic fatty liver disease, we need to consider bariatric surgery as the treatment of choice for this patient population — more specifically patients with a BMI greater than 35 who have other comorbidities or patients with a BMI greater than 40. Our findings provide even more objective evidence of the benefits of bariatric surgery.