Practical Solutions for Diarrhea After Bariatric Surgery

Medically Reviewed by Katelyn J. Mock, US-Registered Dietician (R.D.)

A common side-effect of gastric sleeve or duodenal switch bariatric surgery is diarrhea. People who’ve had the Roux-en-Y gastric bypass surgery (RYGB) may also experience loose stools after bariatric surgery.[1]American Society for Metabolic and Bariatric Surgery, “Bariatric Surgery: Postoperative Concerns“
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This is something one needs to be mentally prepared for after a weight loss procedure. Diarrhea is easier to deal with when the reason behind the same is known.

Reasons for Loose Stools Post Weight Loss Surgery

There is a change in bowel movement after bariatric surgery, but the severity and symptoms differ from case to case.[2]Yves M. Borbely, Alice Osterwalder, Philipp C. Nett et al. “Diarrhea after bariatric procedures: Diagnosis and Therapy” World Journal of Gastroenterology 2017; 23(26): 4689-4700
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  • Alterations made in the duodenal switch can affect bowel movements (BM) and result in diarrhea.
  • Irritation of the colon caused by fatty acids passing into it can also result in diarrhea.
  • The quick movement of relatively undigested food through the digestive tract can also induce diarrhea.
  • Another contributing factor could be sorbitol, a sugar alcohol found in fruits and artificial sweeteners. Since sorbitol doesn’t get absorbed in the digestive tract, it ferments in the colon, thereby resulting in excess gas and loose stools.
  • Some people may have undiagnosed lactose intolerance before surgery which could manifest as diarrhea. Duodenal switch and gastric bypass may unearth that.
  • It could also be Clostridium difficile (C. diff.) colitis or antibiotic-associated diarrhea (AAD).

Tips for Loose Stool Post Weight Loss Surgery

  • Taking Imodium before going to bed may help decrease the number of bowel movements in the morning. It may also delay the onset of BM.
  • The American Society for Metabolic and Bariatric Surgery (ASMBS) recommends a maintenance dose of Imodium for control over the long run.
  • Taking probiotics, such as Lactobacillus Acidophyllus® and Ultraflora® lactose-free, can help restore the colonic flora to its usual state.
  • Even a couple of days of diarrhea after bariatric surgery can result in the loss of nutrients, such as potassium and calcium, from the body resulting in a fainting spell. Some people may also report excessive sweating and dizziness.
  • Since rehydrating after bariatric surgery can be a challenge, do not hesitate to go to the hospital to get some IV fluids if you find it difficult to get more than 32 oz of liquids in a day.
  • Some good fluid options to have on hand on days you feel nauseated, with loose bowels or you end up vomiting are:
    • Pedialyte
    • Gatorade
    • Powerade
  • Treating C. diff. involves reinstating the colonic flora with probiotics.
  • ASMBS recommends taking Flagyl® for 10-14 days to treat AAD.

Important: Before altering your diet, multivitamin intake, and medication regimen, please contact your physician.

If you notice persistent or severe gastrointestinal symptoms such as diarrhea, nausea, vomiting, abdominal pain, or constipation talk to your primary physician about a workup for possible bacterial overgrowth or celiac disease.

This Post Addresses


  1. American Society for Metabolic and Bariatric Surgery, “Bariatric Surgery: Postoperative Concerns
  2. Yves M. Borbely, Alice Osterwalder, Philipp C. Nett et al. “Diarrhea after bariatric procedures: Diagnosis and TherapyWorld Journal of Gastroenterology 2017; 23(26): 4689-4700

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