Research from the University of Bristol, supported by the National Institute for Health and Care Research, has confirmed that gastric bypass surgery is the most clinically and cost-effective treatment for people living with severe obesity.

The decade-long study, named the By-Band-Sleeve trial, involved 1,346 patients and was the largest of its kind. It compared three types of bariatric surgery: Roux-en-Y gastric bypass (Bypass), adjustable gastric banding (Band), and sleeve gastrectomy (Sleeve).

The study found, after three years, that 68 per cent of Bypass patients achieved at least 50 per cent excess weight loss, compared to 41 per cent Sleeve and 25 per cent for Band. Bypass led to greater reductions in comorbidities such as high blood pressure and diabetes, as well as being the most cost-effective option.

Nicki Salter, Somerset NHS FT's research team leader for bariatrics, weight management and endocrinology, said: "For the first time we now have the concrete evidence to tell patients considering bariatric surgery which operation is best out of the three procedures compared.

"This is not only around weight loss and cost effectiveness, but also in terms of quality of life, which perhaps is the most important factor."

Professor of surgery at the University of Bristol, Jane Blazeby, also commented: "Based on the trial findings, we recommend patients electing to have a bariatric and metabolic surgery are advised to have Bypass. Sleeve should be a secondary option when Bypass is not possible. Our evidence does not support Band as standard treatment for people living with sever obesity.

"The hard work undertaken by all the study participants, surgeons, nurses and dieticians means we now have reliable information to inform NHS practice.

"The next challenge is for surgical teams to work with researchers and physicians to conduct a new study that compares surgery to weight loss drugs to create evidence to understand how they compare surgery in terms of weight loss, quality of life and costs."