IBS, SIBO, FODMAP, and the rest of the alphabet

June 28, 2016

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A Certified Eating Disorders Registered Dietitian (CEDRD) with a master's degree in dietetics & nutrition. My passion is helping you find peace with food - and within yourself.

Meet Katy

I am always skeptical whenever clients tell me about food intolerances or that they are on a special diet like FODMAP, gluten-free, dairy-free, vegetarian or vegan.  These types of diets are restrictive which can collude with the eating disorder.  Reality is that most people with eating disorders have some GI issues.  This is what happens when your eating is disordered – it gets out of balance – and it causes your digestive system to get out of balance too.  

Normal eating tends to produce normal digestion, but sometimes it takes several weeks for this to happen.  I find that on average, someone who is really following the nutrition therapy eating plan feels better in 2-6 weeks as the gut has had time to heal.  If GI symptoms are ongoing we might take a look at further interventions from there.  I am careful to avoid any type of unnecessary dietary restriction in clients with eating disorders because it makes recovery so much more difficult. 

However, we can't ignore that many people legitimately suffer from gastrointestinal (GI) issues, ranging from bloating, cramping, constipation, and diarrhea.  It's been estimated that 1 in 5 people suffer from irritable bowel syndrome (IBS)1 which can present with constipation, diarrhea or alternate between the two.  

Some studies are suggesting that the majority of cases of IBS result from small intestine bacterial overgrowth (SIBO)2.  This means that excessive bacteria has grown in the small intestine, which does house some bacteria in a healthy person, but most of our intestinal bacteria should be in the large intestine.  SIBO presents with the same GI symptoms as IBS and can also lead to nutrient deficiencies caused by rapid transit time in which the nutrients don't get absorbed.  Potential deficiencies include fats and fat-soluble vitamins A, D, E and K, as well as B12 and iron3.

I cannot stress enough how important it is to see a doctor to get a diagnosis before self-treating for these conditions.  Many, many things can cause GI symptoms, and it's important to know what you are treating in order to know how.  I have seen so many people self-diagnose and start eliminating things from their diet without any real reason, only to later realize how much unnecessary distress they put themselves through.  

IF you do have a SIBO diagnosis, the treatment is to eliminate the excess bacteria in your small intestine.  This is often done with antibiotics and sometimes a special "elemental" diet that basically starves the bacteria to death.  If you are prescribed to follow a FODMAP diet it is best to work with a knowledgeable RD.  

What is a FODMAP diet?  It is a diet designed to be low in the nutrients that the SIBO bacteria are feeding on – Fermentable Oligosaccharides, Disaccharides, Monosaccharides and Polyols.  When these nutrients aren't properly digested they provide fuel for the bacteria to feast on, which in turn produces the GI symptoms (gas, bloating, cramping, diarrhea, constipation).  

You don't have to look too hard on the internet to find a list of FODMAP foods to avoid.  However, avoiding all of these foods is generally unnecessary.  The RD can help you figure out what foods may be causing you trouble without making your diet too restrictive. This can be ESPECIALLY challenging for someone with an eating disorder.  



1. National Digestive Diseases Information Clearinghouse. Irritable bowel syndrome. NIH Publication No. 07-693. September 2007. Available at:

2. Pimentel M. A New IBS Solution. Sherman Oaks, California: Health Point Press; 2005.

3. Jacob, A. Today's Dietitian. Treatment and Management of SIBO — Taking a Dietary Approach Can Control Intestinal Fermentation and Inflammation. December 2012.  Available at:

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