Bariatric Studies

The following studies are being carried out at the Somerset Foundation Trust.


Gastric Bypass, adjustable gastric Banding or Sleeve gastrectomy surgery to treat severe and complex obesity: a multi-centre randomised controlled trial.

Musgrove is currently participating in the By-Band-Sleeve study – the largest randomised controlled surgical study in the world in the treatment of severe and complex obesity.

This study has been running for eight years. It’s aimed at patients undergoing the three most common types of bariatric surgery for obesity: gastric band surgery, gastric by-pass surgery and sleeve gastrectomy surgery. Currently, we don’t advise which is the best type of surgery to undergo due to lack of credible evidence – and this is the purpose of this study, which is the first to compare operations fully.

Each surgery is slightly different in what it does and how it impacts on weight loss. The initial rate of weight loss varies with the 3 operations but total weight loss is similar 2 -3 years post-surgery.

The bypass and sleeve affect your gut’s hormones, which in turn reduce your appetite; this effect lasts for approximately 18 – 24 months. Patients are taught techniques in this time to help their ability to maintain the weight loss in the long term.

The gastric band is adjustable and affects the vagus nerve in your stomach which sends signals to the brain which reduces appetite and patients are satisfied with small portions of food.

Musgrove was the first site to take part in the study when it opened in 2012 and Southampton also took part in the pilot phase. Due to successful recruitment of the study in the 2 year pilot phase, the study was rolled out to 10 further centres in England. Recruitment to be randomised was completed in September 2019. We have recruited 247 randomised patients at Musgrove Park Hospital and a total of 1351 participants nationally. There are also many other participants involved in non-randomisation arms of the study.

Patients are signed up to the study before they have their surgery and are then randomised into groups to receive one of the 3 operations. After their operation, patients are followed up at Musgrove for three years by our specialist bariatric research nurses and then a further five years by the trial coordinating centre at Bristol University.

On top of their regular routine treatment, patients taking part in the study:

  • Have research blood samples taken before surgery and at specified time points after surgery up until three years after entering the research study
  • Attend study follow up appointments in which physical data is collected.
  • Talk about their experience – recovery, dietary intake, use of the health services and other costs incurred.
  • Fill in quality of life questionnaires and some keep a patient health economics diary.

Metbolomics; a sub-study of By-Band-Sleeve

We are currently recruiting to Metbolomics; a sub-study of By-Band-Sleeve. The metabolomics study aims to find out the impact of weight change and bariatric surgery on the levels of certain blood components. The study involves donating a small sample of blood before surgery and again one year later. Blood samples will be used to measure changes in specific blood components after surgery and during weight loss.

Sub-study end recruitment date: July 2021

Initial results based on Primary data collected in the main randomised By-Band-Sleeve study are anticipated during 2022-2023.

Please visit the By-Band-Sleeve Study page more information about the trial.