Beyond weight loss: The surprising benefits of bariatric surgery

Bariatric surgery is one of the most effective ways to reverse obesity. However, its ability to reverse obesity-related conditions, such as diabetes, and premature brain aging, has been less clear. With thousands of Canadians undergoing weight-loss surgery every year, this question has become increasingly important.

In a CIHR-funded team grant on bariatric care, Dr. André Tchernof, Professor at Laval University School of Nutrition, and his colleague Laurent Biertho, Research Chair at the Quebec Heart and Lung Institute, examined how patients respond to different types of bariatric surgery. “The outcome we were looking for, and the primary question, was the resolution of type 2 diabetes,” he explains. “The hypothesis was that if we know more about the type of surgery and its effect on diabetes, we will be in a better position to choose the right surgery for the right patient because there are different types of operations.”

The study confirmed that bariatric surgery is highly effective for type 2 diabetes, though not all procedures work equally well for every patient. Dr. Tchernof found that biliopancreatic diversion, a more intensive form of weight-loss surgery that reduces the size of the stomach and changes how the body absorbs food, was the most effective option for patients who had been treated with insulin for many years: 50 to 60 per cent experienced diabetes remission. By comparison, patients using insulin who underwent sleeve gastrectomy or gastric bypass had less than a 20 per cent chance of remission. These results show that matching the right surgery to the right patient can make a difference in diabetes outcomes.

The research team also gained new insights into how obesity affects the brain. Obesity is known to accelerate brain aging, possibly due to inflammation and reduced blood flow. What surprised the researchers was that bariatric surgery appeared to reverse this effect.

Four months after surgery, patients’ brains showed characteristics consistent with their chronological age, suggesting that the premature aging associated with obesity may be reversible. This finding points to the previously underappreciated link between metabolic health and brain health.

The researchers also made a major discovery related to gut health. The team found that in people living with obesity, fragments of gut bacteria can leak out of the intestine and enter tissues such as the liver, body fat, and even the bloodstream. Importantly, the extent of this leakage was linked to whether a person had diabetes.

“This had been shown before in mouse models,” explains Dr. Tchernof, “but we were the first to demonstrate it in humans and to publish evidence that bacterial fragments escaping the gut can be detected in tissues, likely contributing to metabolic disease associated with obesity.” Understanding this pathway helps explain why bariatric surgery can rapidly improve diabetes and offers new ways to prevent and treat metabolic conditions.

A fourth major discovery showed that bariatric surgery can quickly improve how the heart handles fat. In people with obesity, the heart takes up too much fat, which can harm its function over time. Remarkably, within just 12 days of surgery, and even before extensive weight loss, the heart’s fat uptake returned to normal. Instead of accumulating in the heart, the fat from food was redirected to body fat, which restored the body’s ability to safely store energy. This indicates that surgery may protect the heart and helps explain how metabolic improvements can occur so quickly after surgery.

Beyond the scientific discoveries, CIHR funding of this team also played a key role in building research capacity. The study served as a critical career steppingstone for five members of this research team, who have since become professors, strengthening Canada’s expertise in metabolic and obesity research.

At a glance

Issue

One in three Canadian adults lives with obesity, a leading risk factor for type 2 diabetes and other metabolic complications. Obesity is treatable. One of the most effective ways is through bariatric surgery. Understanding which type of weight-loss surgery works best for which patient is critical.

Research

Dr. André Tchernof and Dr. Laurent Biertho’s studies showed that bariatric surgery has benefits beyond weight loss. Their team’s major findings are that: patient outcomes depend strongly on the type of surgery; many obesity-related metabolic complications, including type 2 diabetes, are reversible; and the benefits of surgery extend to key organs, including the brain and the heart.