Objective This paper reports the study design, participant characteristics, and recruitment results of By‐Band‐Sleeve, which investigated the clinical and cost‐effectiveness of gastric bypass, gastric banding, and sleeve gastrectomy in adults with severe obesity in the UK. Methods A pragmatic open adaptive noninferiority trial with 3‐year follow‐up was conducted. Participants were randomly assigned to bypass or band initially and to sleeve after the adaptation. Co‐primary end points are weight loss and health‐related quality of life assessed using the EQ‐5D utility index. Results Between December 2012 and August 2015, the study recruited into two groups and, after the adaptation, into three groups until September 2019. The study screened 6960 patients; 4732 (68%) were eligible and 1351 (29%) were randomized; 5 subsequently withdrew consent to use data, leaving 462, 464, and 420 assigned to bypass, band, and sleeve, respectively. Baseline data showed high levels of obesity (mean BMI = 46.4 kg/m2; SD: 6.9) and comorbidities (e.g., 31% diabetes), low scores for health‐related quality of life, and high levels of anxiety and depression (e.g., 25% abnormal scores). Nutritional parameters were poor, and the average equivalized household income was low (£16,667). Conclusions By‐Band‐Sleeve fully recruited. Participant characteristics are consistent with contemporary patients having bariatric surgery, and therefore the results will be generalizable.