BE-CALM: a clinical score to predict weight loss after conversion from sleeve gastrectomy to Roux-en-Y gastric bypass

Conversion from sleeve gastrectomy (SG) to Roux-en-Y gastric bypass (RYGB) may be indicated for patients due to insufficient weight loss or weight regain.

To assess weight loss outcomes and factors predictive of improved weight loss in patients undergoing RYGB after SG and create an algorithm to estimate postoperative weight loss in these patients.

University Hospital.

Retrospective review of patients who underwent conversion from SG to RYGB from 2015 to 2022 was performed, assessing pre-and post-operative weights for each procedure.

114 patients were included (84% female, pre-SG BMI 49.3 ± 10.2). Post-SG, patients achieved a maximum %TBWL of 31.2% ([6.6-58.2] ± 10.1%), %EWL of 56.8%([13.3-97.3] ± 16.4%), and total body weight regain of 53.9%([0.0-144.4] ± 31.3%). Conversion to RYGB resulted in peak %TBWL of 18.8% at 8 months, leveling off at 13.5% thereafter. Factors predictive of greater weight loss post-conversion included higher BMI at time of SG (each 5 kg/m² increase yielded 0.8% greater %TBWL [95% CI 0.5-1%, p < 0.0001]) and peak %EWL ≥ 40% after SG (yielding 5.5% more %TBWL, 95%CI 3.9-7.1%, p < 0.0001). Conversely, those who had ≥ 20% weight regain after SG had 4.1% less %TBWL (95%CI 2.5-5.7%, p < 0.0001) after conversion. These factors were used to create BE-CALM, an algorithm to predict %TBWL one year after conversion to RYGB.

Conversion from SG to RYGB is effective for further weight loss. Patients who have higher starting BMI, ≥ 40% %EWL or ≤ 20% weight regain after SG demonstrate the most effective weight loss post-conversion.