Objectives: To describe gastrointestinal-related side-effects reported following One Anastomosis Gastric Bypass (OAGB).

Methods: A multicenter study among OAGB patients across Israel (n=277) and Portugal (n=111) who were recruited to the study based on time elapsed since surgery was performed. An online survey with information on demographics, anthropometrics, medical conditions, and gastrointestinal outcomes was administered in both countries simultaneously.

Results: Respondents from Israel (pre-surgery age of 41.6±11.0 years, 75.8% females) and Portugal (pre-surgery age of 45.6±12.3 years, 79.3% females) presented mean excess weight loss of 51.0±19.9 and 62.4±26.5%, 89.0±22.0 and 86.2±21.4%, and 89.9±23.6 and 98.2±20.9% (P<0.001 for both countries), at 1-6 months, 6-12 months, and 1-5 years post-surgery, respectively. Median Gastrointestinal Symptom Rating Scale score was similar between time elapsed since surgery groups among respondents from Israel and Portugal (=1.97 and =2.12). A notable proportion of respondents from Israel and Portugal at all time points reported 1-3 bowel movements per day (=62.8 and =87.6%), Bristol stool scale categories which represent diarrhea-like stools (=51.9 and =56.3%), having discomfort due to flatulence (=79.4 and =90.2%), and mild to severe dyspepsia symptoms (=50.5 and =73.0%).

Conclusions: A notable proportion of OAGB patients might experience certain gastrointestinal symptoms postoperatively, including flatulence, dyspepsia, and diarrhea-like stools.