Gastric bypass beat sleeve on every six‑month outcome in a 116,195‑patient registry comparison

A new analysis of the largest national bariatric surgery registry in the United States compared four weight-loss operations against each other and found real differences between them six months after surgery. Gastric bypass did better than sleeve gastrectomy on every outcome the authors reported. The duodenal switch, a far less common operation, produced the largest weight loss and the highest diabetes remission rates of the four.

The study appeared online on September 8, 2026 in Surgical Endoscopy. The authors are based at Johns Hopkins University, Northwest Hospital in Randallstown, Maryland, and Loma Linda University Medical Center. They used the 2023 data file from the Metabolic and Bariatric Surgery Accreditation and Quality Improvement Program, known as MBSAQIP, a registry that collects standardized records from accredited bariatric centers across the country.

The analysis covered 116,195 adults aged 18 to 65 who had a first-time laparoscopic or robotic operation and who had six-month follow-up data on file. Of those, 80,614 had a sleeve gastrectomy, 33,148 had a Roux-en-Y gastric bypass, 1,518 had a biliopancreatic diversion with duodenal switch, and 915 had a single anastomosis duodeno-ileal bypass with sleeve gastrectomy, usually shortened to SADI-S.

Gastric bypass came out ahead of sleeve gastrectomy on every reported outcome

The researchers ran six separate head-to-head comparisons. In each one they paired patients from two operations who looked alike on 47 recorded characteristics, including things measured before, during and after surgery. The idea is to compare people who were similar to begin with, so the operation itself is the main thing left that differs.

Matched against sleeve patients, bypass patients did better on everything reported. Diabetes remission was 64.1% after bypass and 58.1% after sleeve. High blood pressure remission was 41.9% versus 35.8%. High cholesterol remission was 43.0% versus 37.1%. Acid reflux remission was 55.6% versus 44.9%. Every one of those gaps was statistically significant, which means it is unlikely to be chance alone. It does not mean the gap is large enough to matter for any particular person.

Weight loss went the same way. At six months, bypass patients had lost 50.13% of their excess weight, against 43.63% for sleeve patients. Percent of excess weight lost is not the same as percent of body weight lost. It measures how much of the weight above a reference point a patient has shed, so it is always a bigger number than the drop in total body weight. A patient who loses half their excess weight has not lost half their body weight.

The duodenal switch led on weight and diabetes, on 1,518 patients

The duodenal switch produced the strongest numbers in the study. It beat sleeve gastrectomy on excess weight loss, 52.37% versus 37.73%. It beat gastric bypass, 52.35% versus 45.92%. It beat SADI-S, 51.07% versus 45.02%.

Diabetes remission followed suit. The duodenal switch reached 73.3% against sleeve at 59.9%, 73.1% against bypass at 65.6%, and 77.4% against SADI-S at 66.1%. Blood pressure remission was 46.0% against sleeve at 31.6%, and 46.2% against bypass at 37.6%.

Those are striking figures, and they rest on 1,518 patients out of 116,195, about 1.3% of the group. The duodenal switch is a technically demanding operation performed at a small number of centers on carefully chosen patients. Matching on 47 variables cannot erase the difference between a procedure done by a handful of high-volume surgeons and one done at hundreds of centers. The same caution applies more strongly to SADI-S, with 915 patients.

SADI-S came out close to gastric bypass. Excess weight loss was 44.99% versus 44.73%, a difference the authors reported as not statistically significant, with a p value of 0.126. Remission rates for most of the conditions studied were comparable between the two.

Why the same operation shows more than one number here

Readers will notice that sleeve gastrectomy appears with 43.63% excess weight loss in one comparison and 37.73% in another. That is not an error. Each of the six comparisons was matched separately, so each one uses a different subset of sleeve patients, chosen to resemble whichever group they were being compared against. The sleeve patients matched to duodenal switch patients were probably heavier and sicker at the start than those matched to bypass patients. The numbers are only meaningful inside the pair they belong to. They cannot be lifted out and ranked against each other in a single table.

Six months is early, and the hardest questions are left open

The biggest limit is time. Six months captures the steep early part of the weight-loss curve, when nearly everyone is losing. Operations separate from one another over years, not months, and some of the gaps reported here may narrow, widen or reverse. Nothing in this study speaks to weight five or ten years out, which is what most patients actually want to know.

The follow-up requirement matters too. Only patients with six-month data recorded were included, so this is a subset of everyone operated on that year, not the full picture. Patients who stop showing up for appointments are not a random group.

Remission in a registry is also a blunt instrument. It is recorded by staff at each center, definitions can vary from site to site, and missing entries are common. That is different from a trial where every patient gets the same blood tests on the same schedule.

The published abstract reports weight loss and remission. It does not report the trade-offs that usually decide between these operations in practice, including nutritional complications, vitamin and protein deficiency, reoperation rates and long-term surgical risk. Those considerations weigh heavily against the more extensive procedures such as the duodenal switch, which reroutes more of the intestine and requires lifelong supplementation and monitoring. We were not able to read the full text, which is behind a paywall, so we cannot say whether the complete paper addresses them.

None of this settles which operation is right for any individual. That decision turns on starting weight, which conditions a person has, reflux, prior surgeries, how closely they can be followed afterward, and what their surgical team does well. This study adds national six-month comparison data to that conversation. It does not replace it.