Do Sleeve Gastrectomy and Gastric Bypass Change Alcohol Exposure for Three Years?

In a small prospective study, both sleeve gastrectomy and Roux-en-Y gastric bypass were followed by faster alcohol absorption, higher peak concentrations and greater exposure through three years of follow-up. Bypass produced a higher and earlier peak than sleeve at the 12-month comparison, while total exposure was similar. These are group pharmacokinetic findings, not a formula for reconstructing an individual patient’s BAC while driving.

The 2026 BAR-TRIAL adds a longitudinal comparison between two procedures to the site’s earlier gastric-bypass absorption study. It addresses a different question: what changed within patients over time, and how did sleeve and bypass compare?

Repeated oral and intravenous alcohol challenges

The study enrolled 33 adults: 14 underwent bypass and 19 sleeve gastrectomy. Participants were tested before surgery and approximately three, 12 and 36 months afterward. At each occasion, oral and intravenous ethanol challenges occurred on separate days, with their order randomized.

Surgical procedure itself was not randomized. Clinicians selected the operation, leaving the two surgical groups potentially different in ways that could affect comparison.

The oral challenge followed a standardized small breakfast by 60 minutes. Alcohol doses were calculated from preoperative total body water and sex, then the same absolute dose was repeated after surgery. The average dose was approximately 19.6 grams. It was not recalculated downward after weight loss.

Which concentrations were measured?

Peripheral venous specimens were collected frequently, with additional two-, six- and ten-minute postoperative sampling to capture rapid absorption. The paper defines its primary peak outcome as maximum plasma ethanol concentration. These results should not silently be relabeled as evidential whole-blood BAC.

The biochemical measurements used hospital laboratory methods. There were no paired arterial measurements establishing brain exposure, and breath, urine and biomarkers were not substitutes for the serial specimens. The frequent sampling improves peak characterization but cannot guarantee that every person’s exact continuous peak occurred at a sampled instant.

Peak, peak timing and total exposure changed differently

Across follow-up, oral peak concentration and exposure to the last measurable concentration approximately doubled compared with preoperative testing, while time to peak was markedly shorter. Postoperative mean peak times were roughly 10–16 minutes, compared with approximately 26–29 minutes before surgery.

At 12 months, the reported bypass-to-sleeve geometric mean peak ratio was 1.27, while the time-to-peak ratio was 0.69. These describe approximately 27% higher peaks and 31% shorter peak times in the comparison. Total exposure met the investigators’ bioequivalence criterion: the ratio was 0.97 with a 90% confidence interval of 0.80–1.19.

Bioequivalent total exposure does not mean matching peaks or identical time courses. Conversely, a higher peak does not establish that every post-drinking concentration is higher by a constant percentage.

What the intravenous tests contribute

The paper reports no difference in intravenous concentration-time profiles before and after surgery. This supports the authors’ interpretation that altered absorption, first-pass handling and distribution were more important than a major elimination change in the observed oral response.

It does not establish one unchanging personal elimination rate. Nor did the trial directly isolate gastric metabolism as the sole mechanism. Total body water also changed after surgery, and keeping the absolute dose constant increased dose per unit of remaining body water.

Important limits on the three-year finding

Only 73% completed the three-year follow-up. Participants developing alcohol problems were excluded from subsequent testing, and some other participants were lost to follow-up. Later results therefore represent those remaining under observation and may be affected by selective attrition.

The sample was small and predominantly female. No significant sex effect was found for peak concentration or peak timing, but the study had limited power to detect such differences. The fed protocol also limits extrapolation to fasting or other beverage and meal patterns.

The authors describe the changes as permanent. Three-year observations support persistence over that interval, not a demonstrated lifetime duration. The article does not justify calling the effect permanent for every patient.

Implications for a DUI reconstruction

Document procedure type, surgery timing, drinking timeline, food and actual specimen rather than assuming that preoperative drinking experience predicts the postoperative curve. A later test can miss a brief early peak, but this trial cannot supply that missing peak for an individual.

No driving performance or crash-causation endpoint was measured. Neither surgery history nor an average postoperative concentration increase proves impairment at the relevant time. Any case opinion must distinguish observed concentrations from modeled values and acknowledge uncertainty in absorption and sampling.

Primary source

Strømmen M, Dale O, Klöckner C, Tylleskär I. Ethanol pharmacokinetics before and after sleeve gastrectomy and Roux-en-Y gastric bypass: a 3 year prospective study (the BAR-TRIAL). International Journal of Obesity. 2026;50:1573–1580. https://doi.org/10.1038/s41366-026-02113-3.