Percentile-based weight loss benchmarks after sleeve gastrectomy, Roux-en-Y gastric bypass, and duodenal switch: a multi-site cohort study

Why clinicians should know about it

• Picked for Bariatric and Metabolic Surgery (paper of the day, 31 August 2026): Percentile-based weight loss benchmarks after sleeve gastrectomy, Roux-en-Y gastric bypass

Abstract

BACKGROUND: Weight loss after bariatric surgery varies substantially among individuals, yet outcomes are usually reported as averages. Percentile benchmarks may better support patient counseling. OBJECTIVES: To develop percentile-based weight loss benchmarks after primary sleeve gastrectomy (SG), Roux-en-Y gastric bypass (RYGB), and duodenal switch/single-anastomosis duodeno-ileal bypass (DS/SADI). SETTING: Five-campus academic health system, United States. METHODS: Retrospective cohort study of 2730 primary bariatric patients (1796 SG, 663 RYGB, 271 DS/SADI; 2021 to 2026). Of 2928 eligible patients, 2730 (93.2%) had a postoperative follow-up weight; each contributed one most-recent weight (median follow-up 22.8 months; IQR, 9.7 to 36.1). Percent total body weight loss (%TBWL) benchmarks at the 10th through 90th percentiles were estimated using quantile regression adjusted for age, sex, initial body mass index (BMI), procedure, time, and procedure-by-time interaction, with 95% confidence intervals from bootstrap resampling. RESULTS: Among 2730 primary bariatric patients (1796 SG, 663 RYGB, 271 DS/SADI), the three operations tracked closely through the first 6 months, where DS/SADI was not yet distinguishable from SG (P = .14), then pulled apart after the first year and stayed separated through 36 months. For a reference patient (woman, age 42, BMI 45), predicted median %TBWL at 12 months was 24.5% for SG, 30.0% for RYGB, and 33.4% for DS/SADI; by 24 months it was 23.7%, 30.7%, and 36.2%. In practical terms, RYGB ran about 5.5 percentage points ahead of SG at 1 year and 7.0 at 2 years, and DS/SADI led SG by 8.9 and 12.5. But the range matters as much as the average: at 24 months, %TBWL ran from 10.3% at the 10th percentile to 38.1% at the 90th for SG, 16.3% to 44.3% for RYGB, and 17.8% to 47.1% for DS/SADI, so one in ten SG patients lost about 10% or less while another one in ten lost nearly 40%, and a strong SG result matched a typical RYGB. Internal calibration was good (mean error 1.6 percentage points), and the ordering held across sensitivity analyses. CONCLUSIONS: Percentile benchmarks allow a surgeon to show patients what weight loss really looks like after each operation, side by side and out to 3 years, as a range rather than a single number. This is easier to use and more honest for counseling than the average, and it covers the window beyond the first year, when weight loss is still settling.

Abstract as published, via PubMed.