Intensive Weight Loss Intervention Versus Bariatric Surgery for Adults With Severe and Complex Obesity: the LightBAR Randomised Trial

In the LightBAR trial, an intensive weight loss (IWL) intervention will be compared with bariatric surgery. The IWL consists of three phases: 'Induction' phase (week 0-12 after randomisation): total dietary replacement (TDR) programme and behavioural support with weight loss medication (WLM) if rate of weight loss is insufficient. 'Weight loss continuation' phase (week 13-32 after randomisation): progression of dietary programme including reduction in use of TDR products, reintroduction of healthy foods, with behavioural support, introduction of physical activity, WLM (as required). 'Maintenance' phase (week 33-104 after randomisation): Continued healthy diet and physical activity with WLM (if required), with return to induction phase if weight regain occurs induction, weight loss continuation, maintenance. The IWL lasts two years, and includes total dietary replacements, behavioural support, and weight loss medication. Bariatric surgery will be standard Roux-en-Y gastric bypass or sleeve gastrectomy.