Bariatric surgery: study shows long-term benefits in patients with type 2 diabetes

By Rebecca Jenkins

Bariatric surgery for type 2 diabetes leads to superior glycaemic control compared with medical and lifestyle therapies, even in people with class 1 obesity, long-term research shows.

Despite a growing body of evidence, bariatric surgery is generally not recommended for type 2 diabetes unless the person has a body mass index (BMI) of 35kg/m2 or higher, researchers wrote in JAMA.

For this study, the researchers pooled long-term observational results from four US single-centre randomised trials that evaluated the effectiveness and safety of bariatric surgery compared with combined medical and lifestyle management of type 2 diabetes.

Participants had type 2 diabetes and a BMI of 27 to 45kg/m2, which included over one-third of those with class 1 obesity, classified as a BMI of 30 to 34.9kg/m2, or at least 27.5kg/m2 in Asian participants.

A total of 262 of 305 eligible participants enrolled in long-term follow up for the, pooled analysis, with the cohort having a mean age of 49.9 years and a mean BMI of 36.4 kg/m2.

At seven years’ follow up, HbA1c was 1.4% lower in the surgery group than in the medical therapy/lifestyle group, and 1.1% lower at 12 years’ follow up.

More patients in the surgery group achieved diabetes remission throughout follow up than in the medical management arm: 18.2% vs 6.2% at seven years and 12.7% vs 0% at 12 years, respectively.

In addition, fewer antidiabetic medications, including insulin, were used in the surgery group, researchers reported.

The results were consistent across the weight class groups, they noted, showing surgery was equally beneficial to patients with a BMI below and above 35 kg/m2.

Associate Professor Milan Piya, Clinical Academic Endocrinologist at Western Sydney University and Campbelltown and Camden Hospitals, Sydney, said the long follow up provided reassurance that the effects from bariatric surgery were durable.

Professor Piya, who is also Research Lead for the South Western Sydney Metabolic Rehabilitation and Bariatric Program, noted the newer incretin therapies semaglutide and tirzepatide were not available at the time of the studies and that the sample size was not that large.

‘Nevertheless, the results suggest that for those with very difficult to control type 2 diabetes, we can consider bariatric surgery as an option, even in class 1 obesity,’ he told Medicine Today.

Currently, 97% of primary bariatric surgical procedures are conducted in the private health system in Australia, with very limited access to publicly-funded procedures, Professor Piya noted, despite strong cost-effectiveness data.

None of the publicly-funded services offered bariatric surgery for class 1 obesity, he added.

The findings were a reminder to consider bariatric surgery earlier in the disease process of type 2 diabetes, particularly given the greater evidence for remission of type 2 diabetes for those with a shorter duration of diagnosis, and given the multiple stages and barriers involved in accessing the procedure.

‘It would be good to involve an endocrinologist in the decision to refer someone with class 1 obesity for surgery as the evidence is not unequivocal,’ he said.

‘Even for those with class 2 and 3 obesity, first involve someone with expertise in using the newer incretin agents out there; potentially as a bridge to weight loss and improvement in HbA1c preoperatively.’

He said some people might not proceed to surgery if they had a significant improvement in their glycaemic control, or if they were unable to afford the procedure or unable to have it due to comorbidities.

JAMA 2024; 331: 654-664.