Bariatric surgery ‘powerful’ tool for understanding biology of obesity

BOSTON — A physiological regulation of energy balance drives most obesogenic behavior, and bariatric surgery is likely to best option to “rewire the body” to respond to environmental factors in a healthier way, according to a speaker at the Cardiometabolic Health Congress.

Bariatric surgery has unique capabilities that are not seen with other weight-loss options available to patients with obesity, particularly restrictive dieting, Lee Kaplan, MD, a gastroenterologist and professor of medicine at Harvard Medical School in Boston, said during a presentation.

The human body, he said, seeks a stable fat mass “set point,” just as it seeks a stable liver mass and stable red blood cell count. That set point, while often influenced by genetics, is also shaped by environmental factors: abnormal diet, unhealthy muscle that does not produce cytokines, sleep deprivation, stress, disrupted circadian rhythms and medications that induce weight gain.

“Over time, these factors that increase the body fat mass set point get established more firmly,” Kaplan said. “And over time, you change the developmental biology of the human. There is a rewiring of the body in response.”

Dieting downsides

With restrictive dieting, Kaplan said, the body works to conserve energy expenditure as part of an effort to get back to its original fat mass set point, noting that the resulting increase in appetite, stress response and gut peptides all push the body to regain weight.

After bariatric surgery, particularly Roux-en-Y gastric bypass, the opposite effect occurs, Kaplan said: Energy expenditure and satiety hormones go up, whereas appetite, stress and levels of the hunger-related hormone ghrelin go down.

“What this tells us is, in response to restrictive dieting, the body tries to get back to the set point, like with donating blood,” Kaplan said. “In the case of bariatric surgery, you are lowering the (fat mass) set point of the body. On the day of the operation, after the patient wakes up, they haven’t changed their weight, but they will now begin to burn fat to get to the lower set point.”

“Surgery isn’t the only thing that lowers the set point, but surgery is the most powerful thing that lowers the set point,” Kaplan said.

Diabetes data

The various types of bariatric surgery, including Roux-en-Y, vertical sleeve gastrectomy and biliopancreatic diversion, all induce weight loss in multiple ways that can help improve type 2 diabetes and metabolic dysfunction, Kaplan said.

“(The surgeries) change taste, they change central nervous system effects, they change lipid metabolism and, of course, they change carbohydrate metabolism,” Kaplan said. “To improve diabetes, dyslipidemia, hypertension and a whole variety of other metabolic disorders.”

In recent epidemiological studies, Kaplan said, new incidents of type 2 diabetes are substantially reduced in patients undergoing bariatric surgery vs. medical management.

An analysis of the STAMPEDE trial, he said, suggested that sleeve gastrectomy and gastric bypass improved HbA1c at a greater and more prolonged rate vs. medical therapy.

Five-year data from STAMPEDE, not yet published, shows that patients who underwent gastric bypass maintained their change in weight and HbA1c improvement at a greater rate vs. those who underwent pharmacological interventions, Kaplan said; 45% of those who underwent bariatric surgery were still not using diabetes medications.

S urgery recommendations

In June, 45 international professional organizations formally recommended that bariatric surgery be considered part of the standard of care in the treatment of type 2 diabetes for certain patients. The statement marks the first time that bariatric surgery was recommended as a treatment option specifically for diabetes.

The joint consensus statement, released following the Diabetes Surgery Summit (DSS-II), recommended metabolic surgery to treat patients with type 2 diabetes and either class III obesity (BMI 40 kg/m²) or class II obesity (BMI 35 to 39.9 kg/m²) when lifestyle and medical therapy fail to control hyperglycemia. Researchers also recommended bariatric surgery be considered for patients with type 2 diabetes and a BMI between 30 kg/m² and 34.9 kg/m² if those patients cannot maintain glycemic control with oral or injectable medications.

However, even though the recommendations were purposefully made to be “conservative and evidence-based,” there is still a resistance to surgery among many, Kaplan said.

“I think that comes from challenges to obesity care,” Kaplan said. “The perception that obesity is not a disease. You can’t separate obesity from diabetes in the minds of many people. If obesity is not a disease, then perhaps we ought not to be treating [diabetes] with an operation that was originally developed for obesity.

“Many people misapprehend the causes and complications of obesity,” Kaplan said. “They conclude that it’s the primary responsibility of the patient.”

Those perceptions, Kaplan said, discourage patients from seeking care for obesity, among other challenges, including inadequate knowledge of the benefits of bariatric surgery, and insurance and financial constraints.

Going forward, there needs to be wider communication about obesity and all available treatment options with both health care providers and the public, Kaplan said.

“Medical and surgical care for both obesity and diabetes need to be used cooperatively,” he said. – by Regina Schaffer

Reference:

Kaplan L. A Dialogue Between the Experts: The Newest Evidence on Metabolic Surgery. Presented at: Cardiometabolic Health Congress; Oct. 5-8, 2016; Boston.

Disclosure: Kaplan reports receiving consultant fees from Apollo Endosurgery, Astra Zeneca, Ethicon, Fractyl, Gelesis, GI Dynamics, Janssen, Medtronic, Novo Nordisk, Rhythm, USGI Medical and Zafgen.