Changes in gastrointestinal symptoms and food tolerance 6 months following weight loss surgery: associations with dietary changes, weight loss and the surgical procedure.

Background: Gastrointestinal (GI) co-morbidity is common in obese patients, but the effect of weight loss surgery on GI symptoms is incompletely elucidated. The aims of the present study were to explore changes in GI symptoms and food tolerance following weight loss surgery and to study whether such changes were associated with dietary modifications and/or the type of surgical procedure [Roux-en-Y Gastric Bypass (RYGB) versus Vertical Sleeve Gastrectomy (VSG)].

Methods: Participants: Patients with morbid obesity scheduled for weight loss surgery.The patients filled in paper-based questionnaires addressing diet, GI symptoms (bloating, pain, satiety, constipation and diarrhea) and food tolerance/quality of alimentation (satisfaction about current food intake, tolerance to specific foods and frequency of vomiting/regurgitation/reflux) 6 months prior to and 6 months after the surgery. Patients with pre-existing major GI co-morbidity or previous major GI surgery were excluded.

Results: Fifty-four patients (RYGB/VSG: 43/11) were included. Constipation and satiety increased and food tolerance decreased significantly after the surgery (all -values < 0.05). The increase in satiety was significantly more notable after VSG than after RYGB ( < 0.05).The increase in satiety also correlated with an overall reduction in food tolerance (rho: -0.488,  < 0.01). Divergent changes were seen in the frequency of vomiting/regurgitation/reflux, with a decline after RYGB ( = 0.01) and an increase after VSG ( = 0.06). Intakes of energy, macronutrients, fiber and fluid decreased significantly after the surgery (all -values < 0.05), but did not correlate with the changes in constipation, satiety or food tolerance (all -values > 0.05). Pre-operatively, total energy intake correlated with bloating and abdominal pain (rho = 0.343 and 0.310 respectively,  < 0.05 for both), but these correlations did not persist 6 months after the surgery (rho = 0.065 and 0.054 respectively,  > 0.05 for both).

Conclusion: A high caloric intake may explain some of the GI symptoms experienced by non-operated obese patients. The worsening or new-onset of symptoms post-surgery is likely due to anatomical or physiological alterations following surgery. The increase in satiety and the decrease in food tolerance are likely explained by the restrictive nature of the surgeries, as satiety increased more after VSG than after RYGB and correlated with an overall reduction in food tolerance.