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Small Intestinal Bacteria Overgrowth (SIBO) & Eating Disorders

Updated: Oct 25, 2023

In general, the small intestine is free from bacteria. Small intestinal bacterial overgrowth (SIBO) is a condition in which the small intestine is colonized by excessive bacteria that are normally present in the large intestine. When the gastrointestinal system slows down, a common issue among individuals with eating disorders, bacteria can take over the small intestine and causes problems. The majority of patients with SIBO present with bloating, flatulence, abdominal discomfort, or diarrhea.

The mind-body connection is very strong among individuals with eating disorders. Clinicians not trained in eating disorders can diagnosis individuals with ‘nothing being wrong’ or ‘it’s just the eating disorder’. Yes, sometimes symptoms of bloating, flatulence, abdominal discomfort, and diarrhea are related to the eating disorders but not always. Differentiating pathology such as irritable bowel syndrome (IBS) often diagnosed in individuals with eating disorders from the complications of malnourishment and introducing food back into one’s diet during recovery is remarkably complicated. Complicating things even more, SIBO is often misdiagnosed as IBS.

Most patients with established SIBO have a known underlying condition or other risk factors including:

· Eating Disorders

· Irritable Bowel Disease

· Older age

· Diverticulosis

· Surgical procedures (e.g. gastric bypass)

· Adhesions from surgery or radiation

· Small intestine injury

· Fistulas

· Medical conditions: diabetes, lupus, connective tissue disease

· Certain medication use: narcotics, antibiotics, proton pump inhibitors


The Hydrogen/Methane Breath test with lactulose or glucose challenge is used to diagnose SIBO. This test can be performed in a lab, but take-home collection kits have become available and more commonly used. The test is performed after the cessation of certain medications that interfere with regular intestinal motility, digestion and microflora balance. A 1-2-day preparation diet is also required that is VERY restrictive, therefore I rarely recommend breath testing for my patients with eating disorders. It is often safer to just treat for SIBO in patients with eating disorders rather than promoting a restrictive diet even if only temporary.


Therapies for SIBO include non-antibiotic and antibiotic treatment regimens. Antibiotic therapy to treat SIBO includes Rifaximin for 14 days. This antibiotic is well tolerated and has been demonstrated to be effective in the treatment of SIBO. Rifaximin can be expensive and may require more than one treatment. Some patients with SIBO have persistent symptoms after initial antibiotic treatment or have recurrent SIBO within nine months of antibiotic treatment. A second course of antibiotics is reasonable if only partial improvement of symptoms or early recurrence (<3 months) occurs. Persistent symptoms after two courses of antibiotic therapy or progressive symptoms should prompt further evaluation for alternative diagnoses. Alternative antibiotics for treatment of SIBO are also available these include norfloxacin, ciprofloxacin, metronidazole, trimethoprim sulfamethoxazole, tetracycline, or amoxicillin-clavulanic acid.

Non-antibiotic treatment for SIBO should be considered in most patient especially those who are not officially diagnosed through breath testing. Herbal medications may be less problematic for gut health than antibiotics and have a lower risk of causing a serious condition called C. Diffi colitis. Herbal antibiotics that are helpful for SIBO include FC Cidal and Disbiocide prescribed as 2 caps of each 2 times a day for 30 days. Another herbal remedy which can be helpful for SIBO symptoms include Atrantil, 2 caps twice daily for 30 days than 2 caps daily. Sometimes symptoms can worsen within the first few weeks of herbal treatment as the small intestinal bacteria die.

There is limited data to support probiotics in the treatment of SIBO so I do not regularly recommend its use to my patients. See my article on the use of probiotics and eating disorders for more information. Deficiencies of micronutrients are common in eating disorders and can contribute to SIBO symptoms. Deficiencies of vitamin B12, fat-soluble vitamins, iron, thiamine, and niacin can be associated with severe SIBO and should be corrected when present. Ideally these deficiencies should be treated as an individual with an eating disorder is properly regularly nourished. Replacement of micronutrients and vitamins should only be done with guidance from your physician.

SIBO symptom recurrence is quite common after antibiotic treatment. Antibiotics may not be a long term solution for SIBO if there's an underlying condition (eg nutritional deficiency, motility disorder, anatomical intestinal abnormalities). If rifaximin doesn't relive symptoms consider repeating at a dose of 550 mg 3 times a day alone or in combination with neomycin 500 mg 2 times a day for 14 days. Rifaximin has a good safety profile, protects the intestinal natural micro biome, and doesn't cause antibiotic resistance. Wait approximately four weeks before repeating rifaximin. Althoguh I never encourage restrictive diets a diet higher in protein and lower in carbohydrates may be helpful. When indicated consider supplementing fat soluble vitamins (A, D, & E), B vitamins, and iron.

Low fermentable oligo-, di-, and monosaccharides and polyols also known as the FODMAP diet is commonly recommended for the treatment of IBS and SIBO. FODMAPs are short-chain carbohydrates that are poorly absorbed and are osmotically active in the intestinal lumen where they are rapidly fermented by small intestinal bacteria. A diet low in FODMAPs has been thought to improve bloating and gas in patients, however, evidence to support a low FODMAP diet in the prevention or management of patients with IBS and SIBO are lacking. Other diets such as the elemental diet have also been used for SIBO treatment but with little evidence to show improvement. I do not recommend pursing ANY restrictive diet for patients with or recovering from an eating disorder.



Chedid V, Dhalla S, Clarke JO, Roland BC, Dunbar KB, Koh J, Justino E, Tomakin E, Mullin GE. Herbal Therapy Is Equivalent to Rifaximin for the Treatment of Small Intestinal Bacterial Overgrowth. Global Adv Health Med. 2014;3(3):16-24

Carr J, Kleiman SC, Bulik CM, Bulik- Sullivan EC, Carroll IM. Can attention to the intestinal microbiota improve understanding and treatment of anorexia nervosa? Expert Rev Gastroenterol Hepatol. 2016;10(5):565-9.

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