Diarrhea is not a typical side effect of the vertical sleeve gastrectomy or roux-en-y gastric bypass. It could be related to lactose intolerance. When checking the food labels for lactose, also look for ingredients like butter solids, casein, lactate, milk derivative, opta, rennet casein, simplesse, and whey protein concentrate. Eating and drinking together could also cause diarrhea because food is being flushed through the GI system at a faster rate.

Other tips to help resolve diarrhea include:

  1. Avoid sugar alcohols (erythritol, mannitol, xylitol, etc.)
  2. Chew food thoroughly
  3. Limit sugar intake to 10gm per serving and limit fat to 5gm per serving
  4. Decrease caffeine intake
  5. Try a probiotic with Lactobacillus

Please reach out to your medical team if symptoms persist.


Isom, K. A., & Majumdar, M. (2022). Pocket guide to bariatric surgery. Academy of Nutrition and Dietetics.