Intermittent Fasting: An Important Part of the Treatment for Small Intestinal Bacterial Overgrowth/IBS

Dr. Leah Hassall, ND

Small intestinal bacterial overgrowth (SIBO) is a condition in the gut where the bacterial population in the small intestine greatly exceeds the amount normally found there causing gas, bloating, diarrhea and/or constipation. It is now generally accepted that IBS is not caused by stress, but by bacterial dysbiosis and more specifically, SIBO. There are several processes that are thought to play a role in developing SIBO, but one of the most important is when there are problems with the way that the small intestine moves food and bacteria through it.

After we eat a meal, the human gastrointestinal system (mouth, stomach, small intestine and large intestine) starts a cascade of actions that function to break down and digest food into small pieces. Ultimately, after all of the churning, mixing and chemical dissolving, we absorb the nutrients in the small intestine and form stool in the colon. Waves of motion are initiated in the muscular lining of the digestive system to help propel food materials in the “southerly” direction. Even during periods without food or fasting, something known as the migrating motor complex (MMC) is formed every 90-120 minutes. The MMC is a series of waves of electrical activity travelling through the muscle of the gut that acts to sweep debris, including bacteria, from the small intestine into the colon where it belongs. Without this “housekeeping” phase operating properly or at regular intervals, studies show that it can predispose you to SIBO. If we think about it, when food is allowed to sit stagnating in the gut, bacteria will be able to spend lots of time decomposing it and producing gas. This is what is causing the uncomfortable bloat!

So, what does all of the mean for people with SIBO/IBS or even just mild bloating after meals? In order to maximize the time that the MMC is doing its housekeeping work, we want to make sure that we are entering into a fasting stage between meals. The way to ensure that that is happening is to eat smaller meals and fast for at least 3 hours between meals. This means no snacking or grazing – just water and medications for 3 hours. There are other benefits to intermittent or short-term fasting; including increasing insulin sensitivity. Insulin desensitization is a key problem in metabolic syndrome, obesity and type II diabetes. Keep in mind that therapeutic fasting for health conditions should be monitored by a licenced health care professional. Intermittent fasting is used as part of a multifaceted treatment plan for SIBO involving herbal medicines and pharmaceutical antibiotics to address bacterial overgrowth as well as long-term dietary changes and working on getting that migrating motor complex up and running again!


Dukowicz, A. C., Lacy, B. E., & Levine, G. M. (2007). Small Intestinal Bacterial Overgrowth: A Comprehensive Review. Gastroenterology & Hepatology3(2), 112–122.

Husebye, E., Skar, V., Høverstad, T., Iversen, T. & Melby, K. (1995). Abnormal intestinal motor patterns explain enteric colonization with gram-negative bacilli in late radiation enteropathy. Gastroenterology, 109(4):1078-89.

Jacobs, C., Coss Adame, E., Attaluri, A., Valestin, J., & Rao, S. (2013). Dysmotility and ppi use are independent risk factors for small intestinal bacterial and/or fungal overgrowth. Alimentary Pharmacology & Therapeutics37(11), 1103–1111.

Pimentel M, Soffer EE, Chow EJ, Kong Y, Lin HC. (2002). Lower frequency of MMC is found in IBS subjects with abnormal lactulose breath test, suggesting bacterial overgrowth. Dig Dis Sci, 17(12):2639–43.

Takahashi, T. (2012). Mechanism of Interdigestive Migrating Motor Complex. Journal of Neurogastroenterology and Motility18(3), 246–257.

Ghoshal, U. C., Shukla, R., & Ghoshal, U. (2017). Small Intestinal Bacterial Overgrowth and Irritable Bowel Syndrome: A Bridge between Functional Organic Dichotomy. Gut and Liver11(2), 196–208.