It was 2011, and I was helping a researcher perform a DXA scan on a patient who had undergone gastric bypass surgery five years earlier. We were short on time before the next study participant would arrive, so my plan was simply to collect the information the researcher needed and then send the patient on for blood sampling. To break the silence while she was getting dressed, I asked her how she was doing.
Up to that point, my impression was that she must be one of our success stories. She had reached a normal weight and had stopped taking medication for hypertension. I suppose this was the image I was hoping to have confirmed by asking what I thought was a harmless question. Instead, she burst into tears, and I immediately realized that my schedule was about to fall apart.
In the minutes that followed, she told me a story I had not been prepared for. Her life was starting to unravel because of alcohol problems. She said that alcohol had never been an issue for her before, but that the problems had followed the surgery, which she described as the switch that had turned everything on. As a nurse with no particular expertise in substance use or addiction, there was little I could do beyond showing her that I was listening. But given how clearly she perceived a causal link between the operation we had provided and the problems she was now facing, I promised her that I would look into it.
That meeting with a single patient pushed my professional life in a new direction. At the time, the scientific literature was very limited and offered little support for a possible connection. Two years later, I initiated the BAR-TRIAL project, designed to examine how two different bariatric procedures affect the pharmacokinetics of alcohol, both in relation to each other and over the long term. Around the same time, I developed an educational programme for patients. Since 2013, that programme has been continually updated with increasingly evidence-based knowledge about the mechanisms involved and about how alcohol problems after bariatric surgery might be prevented.
The study became a journey in itself. The first milestone was obtaining ethical approval for a study that involved administering alcohol to patients, both orally and intravenously. To my considerable surprise, the ethics committee had few objections. The next challenge was recruiting enough participants. Since our hospital performed relatively few bariatric procedures, the study was eventually expanded to include additional hospitals. Participants were given thorough information about our emerging concerns regarding a potential downside of surgery, but they still chose to take part.
In the protected setting of the hospital’s clinical research ward, the patients arrived early in the morning for a standardized breakfast before the drink was served. None of them were deterred by this first test round, and they returned three months after surgery for a new session at the university hospital. The alcohol dose was the same as before surgery. This had an important educational purpose: to show patients how continuing the same pattern of alcohol consumption that had seemed unproblematic before surgery could have very different consequences afterwards. And this became visible. Even the most reserved participants suddenly became talkative, and many good stories were shared during the hours the intoxication lasted.
The good atmosphere during the test sessions stood in stark contrast to the seriousness underlying the study. Along the way, several participants had to be withdrawn because they developed alcohol problems — a sobering reminder of the reality that too many bariatric patients experience.
Now, the results of the study are out. We were able to complete a thorough comparative study of the two most common bariatric procedures, and we also took the time to examine the long-term effects. Much of the research so far has focused on gastric bypass as the operation that affects alcohol metabolism. Although our study also finds that the effect of bypass is somewhat greater than that of sleeve gastrectomy, it is important that this does not overshadow the fact that both operations have a substantial physiological effect — one that, for patients, may mean an increased risk of alcohol-related problems.
Let us use this knowledge to improve patient selection and follow-up after bariatric surgery, so that this treatment can become safer.
https://doi.org/10.1038/s41366-026-02113-3