Obesity raises the risk of developing liver disease later in life. But a study published Tuesday in JAMA Internal Medicine found that bariatric surgery to reduce abdominal obesity improves liver function in people with “hepatic steatosis,” a buildup of fat in the liver, while at the same time reducing overall mortality from liver disease.
In addition, bariatric surgery is known to help patients with diabetes control blood sugar levels, according to doctors who have published a corresponding editorial in the journal.
Overall, the study, published in a joint effort between gastroenterology and hepatology researchers at the Harvard T.H. Chan School of Public Health and Brigham and Women’s Hospital, involved a database of patients who were either morbidly obese or moderately obese, at a body mass index of over 40. All of the participants also had bariatric surgery, usually at the Boston VA Medical Center, an independent branch of the VA health system. Of the patients who received bariatric surgery, the average age was 55 years old and the average life expectancy was 78 years, the study found.
Readers of the study will have to recall exactly what the team called the “well-understood laws of biology that govern the physical appearance of fat and what they tell us about the risk of developing metabolic syndrome and several serious complications of obesity.” The team summarized this in the accompanying editorial, in which Dr. Steven C. Narod, a professor of medicine at Dartmouth and co-author of the editorial, likened the link between abdominal obesity and liver fat to that between height and metabolic syndrome.
Bariatric surgery is defined by the American College of Surgeons as a surgery to reduce the size of the stomach so that patients can eat less and lose weight and body mass. Generally, when a patient gets bariatric surgery, they’ll be informed beforehand that they have an elevated risk of developing liver disease, and subsequently gain a vast amount of weight over time.
The researchers weren’t able to distinguish between changes in the liver in the patients who got bariatric surgery, those who were obese at the start of the study and those who weren’t. And even after controlling for previous liver disease, there was no evidence that bariatric surgery improved the liver functions of patients who were obese and had had lap-band surgery, a type of bariatric surgery.
But the patients who were obese and didn’t have lap-band surgery but got other types of bariatric surgery, specifically gastric bypass surgery, had reduced liver fat without improving their survival. These patients had raised liver fat before bariatric surgery but saw their liver fats reduced once they got the surgery. Narod in the editorial wrote that it is possible that the effect on liver fat results from the surgery, not from the fat content of the liver before the surgery.
Narod suggested that the reason to get the surgery regardless of the effects on liver fat was “determined from data indicating that a reduced risk of liver disease lowers overall mortality associated with liver diseases, and thus, influences costs and quality of life.”
This study “supports the notion that bariatric surgery has a cost-effective clinical impact on both overweight and obese adults who are in or approaching the advanced age of 60,” according to the editorial.
About 30 million people in the United States are considered obese, a category in which the body mass index of a person equals 30 or higher. Other obese adults fall into the category of “normal-weight obese” and have a BMI of 25 or more. Obese people with a BMI of 30 or higher are considered morbidly obese.
The study is the most recent to document how bariatric surgery is considered to be effective in reducing the risk of death from both fatty liver disease and liver cancer. In January, researchers from the University of Washington published a study looking at data from 22 previous studies and published the results that revealed bariatric surgery was associated with decreased mortality and decreased liver cancer mortality.