During my SIBO journey, managing my weight was a monumental task. I had a very rapid and scary weight loss of about 25 pounds in a 4-month period. And I was at a healthy weight before the loss so I looked and felt quite emaciated when I reached my lowest weight.

What was even scarier than my severe weight loss was how others perceived my weight loss. There were 3 main reactions that were all detrimental to my healing journey.

First, my immediate family was legitimately worried I had an eating disorder. Their intervention strategy was not helpful, because I didn’t have an eating disorder! I just wasn’t absorbing food and felt sick when I ate.

Instead of helping me figure out why I was in so much pain and not absorbing food, they were incessantly nagging me to eat cookies and high calorie foods that I knew would make me sick! I felt misunderstood and isolated from my family in the early stages. But eventually, they realized that my weight loss was not desired and started to support my gut health recovery.

Second, some of my friends and acquaintances had an even scarier reaction then my family. Many of them praised my weight loss!! I constantly heard compliments like “you look so good” or “I wish my arms were as skinny as yours”. I felt like death, but at least I looked good was the disturbing vibe I would get from some of my friends and co-workers.

Third and the scariest reaction of all, my conventional doctors seemed unconcerned by my severe weight loss. I think it is common for doctors to ignore weight loss if the patient still falls in the normal BMI range, which I did (just barely).

In fact, malnutrition is commonly under-diagnosed in hospitals. The inability to flag malnutrition demonstrates the failure of the conventional medical system to fully recognize the critical role nutrition plays in health and disease. How is nutrition supposed to be viewed as a valuable tool in disease prevention and management when doctors only average about 20 hours of nutrition education in their whole medical training?

Far too often doctors’ lack of nutritional awareness allows malnutrition to slip through the cracks. But a good dietitian or functional practitioner understands the consequences of unintentional weight loss and will act with a sense of urgency when they see rapid weight loss in their patients. But, many SIBO sufferers are left to their own devices to halt any weight loss, because they can’t afford or they don’t have access to a dietitian or functional practitioner.

But, our inability to recognize rapid weight loss as a serious problem is even more rooted in our societies idolization of thinness than the failure of our docs to diagnose malnutrition. As a culture, we equate thinness with health. Our hungry runway models strut down the cat-walk with BMIs under 18 and show clinical signs of malnutrition.

When we live in a country that strives to look malnourished, it is no surprise that we can fail to see weight loss as a serious problem. I have seen some in the SIBO community even celebrating their steep weight loss. That always terrifies me!

Losing large amounts of weight before and during treatment should be seen as a warning sign (not to be ignored or celebrated)! If you are experiencing uncontrollable weight loss, you are probably either not absorbing the food you are eating and/or not eating enough calories.

SIBO patients are at high risk for losing weight due to three reasons:

  • The overgrowth is disturbing optimal digestion and absorption. In the case of SIBO, you aren’t what you eat….you are what you absorb.
  • SIBO symptoms (nausea, fullness, reflux etc) may make it more difficult to eat the right amount of calories.
  • Overly restrictive diets can make it easy to under eat. Nothing sounds appetizing when you are eating the same 10 foods.

How to determine if you are losing too much weight??

Weight loss criteria for the diagnosis of malnutrition for chronic illnesses by the American Dietetics Association are:

  • equal to or greater than a 5% loss of body weight in 1 month
  • equal to or greater than 7.5% loss of body weight in 3 months
  • equal to or greater than 10% loss of weight loss in 6 months
  • equal to or greater than 20% loss of weight loss in 1 year

Malnutrition refers to the deficiencies, excesses or imbalances in a person’s intake of energy and/or nutrients. If you are not eating and/or absorbing enough of food, you can easily become malnourished.

I lost 11 % of my body weight in the first month and about 18% of my body weight in total unintentional weight loss, which should have raised some alarms with my physicians. But, my doctors didn’t really take my weight loss that seriously, because I still had a normal BMI. Any dietitian would have clearly classified me as malnourished. Based on my interactions with others in the SIBO forums, many SIBO sufferers would meet the criteria for a malnutrition diagnosis.

If you meet this criteria, make sure to bring it up to your doctor or health care practitioner. If they wave off your concerns, than you should find a new doctor!

The consequences of being Malnourished with SIBO!

Whether the malnutrition stems from chronic under eating or from malabsorption, it is going to be impossible to heal from SIBO if you are starved of nutrients! I want to highlight the two biggest repercussions of chronic undernourishment and how that hinders SIBO recovery:

1. Malnutrition is disastrous on your hormones.

When we are underfed, our chronic stress response (the HPA axis) becomes activated and cortisol levels will start to rise. High cortisol levels will down regulate thyroid hormone activation and synthesis, which will slow down your metabolism. This down regulation of the metabolism may have developed as an adaptive response to food scarcity. Your body is essentially trying to slow the burning of your fuel while supplies are low.

Lower thyroid hormone activity is very problematic when trying to clear SIBO. Hypothyroidism caused by chronic stress activation and a general lack of nutrients from malnutrition will slow the motility of food through the GI tract. With motility impaired, the small intestine is a ripe environment for an overgrowth.

In addition, HPA activation will further promote a SIBO friendly environment by reducing blood flow, enzymatic release and nutrients to the gut impairing digestion and weakening gut barrier function. Therefore, chronic stress activation from malnutrition can wreak havoc on the gut.

Sex hormones will also plummet if your percentage of body fat becomes too low. Leptin is a hormone produced by our fat cells that tell our brains that we have enough fuel (energy reserves aka fat) stored in our bodies. It sends satiety signals to the brain to tell us to put the fork down.

But as we lose body fat, leptin levels fall and signal to your brain that energy stores are low. Since reproduction is the most energy expensive process a human can invest in, the brain will suppress sex hormone synthesis when leptin is low to prevent wasting scarce resources.

You can’t have babies if your body is starving! Low sex hormones from malnutrition and low leptin levels is a huge reason why woman with SIBO lose their periods when they lose too much weight.

If you lost your cycle and have lost some weight when you started a restrictive SIBO diet, you may not be getting enough calories or nutrients to support hormone synthesis.

2. Nutrient deficiencies are eminent and will prevent healing

The fewer calories and nutrients you are consuming/absorbing the greater the chances are that you aren’t meeting your bodies needs. SIBO impairs absorption on its own and when this is paired with undereating caused by an overly restrictive diet nutrient status is hit doubly hard.

From a macronutrient level, you need enough calories to provide you with fuel for energy metabolism, immune function, repairing the GI tract, hormone function and to spare your muscles from wasting.

In particular, eating enough protein is crucial for maintaining and repairing the intestinal barrier and to maintain muscle mass.

Carbs are important to feed brain cells and RBCS, to support hormone function and to spare protein from being broken down from the muscles to be used to make glucose.

Micronutrient deficiencies will also develop when you are undereating. The fewer the calories you eat/absorb the harder it is to maintain proper vitamin and mineral levels. And you need micronutrients to heal from SIBO!!

Adequate levels of macro and micronutrients are essential for proper gut function. In particular, the immune system of the gut will start to atrophy if proper nutrients aren’t available to support it’s function.

Secretory IgA is an antibody found in the mucous layer above the gut lining that serves as the first line of defense in protecting us from toxins and pathogenic microorganisms that we consume. In terms of SIBO, IgA is essential for fighting off and preventing overgrowths of bacteria in the small intestine. When IgA becomes low, bacteria, toxins and food will bypass the mucosa causing an immune response which creates an inflammatory cascade in the body.

Kiran Krishnan, a crazy smart microbiologist and gut health expert, says that when individuals with gut issues and food sensitivities limit the diversity of their diet, their secretory IgA usually declines. He attributes this mostly to nutrient deficiencies that ensue from a restricted diet. Zinc, vitamin C, selenium, choline, glutamine, glycine and omega 3 fatty acids are key nutrients for IgA formation.

If your immune system in the gut is on the fritz from lack of nutrients, you can guarantee that your SIBO is not going to clear any time soon. Running some tests to check nutrient levels is a good idea if you can afford it. You may require some supplemental nutrient support during your treatment until you can adequately meet your needs with a diverse diet.

Why are you losing weight? Are you under-eating? Not absorbing?

If you are struggling to maintain your weight, you should determine if the weight loss is due to problems with absorption or from too few calories. These are also not mutually exclusive. I think many SIBO sufferers are both experiencing impaired absorption and eating too few calories. Naturally their could be some level of malabsorption if SIBO is active.

I think a good first step is to rule out any deficiencies in absorption. The easiest and cheapest way to assess this is to check out your poop! Undigested food stuff in your stool can be a good indication that you aren’t absorbing properly. Oily, pale and malodorous poop can also indicate malabsorption. Stools that float and are harder to flush can indicate malabsorption too.

A comprehensive stool analysis can also give you an idea about your absorption capacity. Levels of fecal fat and protein breakdown products found in the  your stool can indicate if you are absorbing properly. Pancreatic elastase can aalso indicate any digestive enzyme inefficiencies that would hinder optimal digestion and absorption.

Nutrient deficiencies can indicate malabsorption, especially iron and B12. If you are eating plenty of meat and are struggling with anemia, I would suspect malabsorption.

If  absorption is deemed suboptimal, you should work with a functional practitioner to determine the cause of the malabsorption. It could be due to an unsuccessful clearance of SIBO. Some digestive support and nutritional supplementation may be necessary to address digestive and nutritional deficiencies while you are digging to the bottom of your absorption issue.

Once you have a picture of your absorption ability, you then should determine if you are eating enough calories. I definitely was unintentionally under-eating when I switched to the SCD/Low Fodmap combo when I first started my treatment. Since my diet was much lower carb than my typical diet, I underestimated the amount of fat I needed to add into my diet to compensate for the missing calories from carbs.

Plus, the diet was so restrictive that I started to dread eating. I was so bored with the limited variety. When nothing sounded good, I would only eat a small snack or I wouldn’t eat at all.

Based on what I’ve observed in the SIBO community, I think that it is under-eating is quite common when switching to a lower carb or SIBO style diet.  If you started unintentionally losing weight when you began a restrictive diet, I would suspect that you are not eating enough calories.

To confirm that you are under-eating, track your calories for 3-7 days to get an idea of the average calories you are actually eating. I find the USDA SuperTracker to be a useful tool when trying to track calories.

You can compare your average calorie intake to your estimated calorie needs using an online calorie calculator. If you are chronically eating less than your estimated needs, then you would benefit from increasing your calorie intake.

There are also some common symptoms of under-eating such as hair loss, feeling cold, sleep problems, blood sugar swings, mood swings and constipation. Check out this article written by Laura Schoenfeld, an registered dietitian, to learn more about the signs of undereating.

Bottom Line:

Malnutrition during SIBO treatment from malabsorption and/or under-eating can derail SIBO recovery. You can not heal from SIBO if your body is starving.  Losing a couple pounds is probably not a big deal. But if you experience moderate to severe unintentional weight loss, I would work closely with a medical professional to stabilize or regain weight.

Thanks for reading!! If you liked this post, please like the SIBO diaries on Facebook so that you can be notified when I post new content.

Until next time!!

Are you struggling to maintain your weight while you battle SIBO?

I can help! 






  • Thank you for running such an informative website and for bringing some occasional levity to this topic. You have helped me a ton.

    Have you found any digestive support enzymes that you think are particularly helpful? For digestion, I am taking Megaspore, which I know has been tremendously helpful, betaine hcl pepsin, which I’m not sure is doing anything for me, and Restore, which I just started. I eat plenty (following AIP, while mindful of certain problematic FODMAPs), but lost a ton of weight before starting the diet and I just can’t put on any weight despite months of work. I know you can’t give med advice (I am on a waiting list to see a practitioner), but you are so knowledgeable, I just hope to hear your thoughts. Thank you!

  • I have had a hormone test done, and mine hormones are like you describe. I hope the creams will help. To carm things down. Tanks for the sharing your experience.

  • I feel like my journey in healing SIBO has been very similar to yours. One of your last posts you talked about how you were very strict with the diet and how you almost became obsessive about it but how you were quite depressed while doing it. I was the same. I was so depressed that I felt like I was crying constantly. Then reading your post about weight loss sounds again very similar to what I went through. I lost a lot of weight fast. I had a lot of people compliment me on how skinny I got. However I did not feel attractive at all. In fact I thought I looked a lot like my Father did when he was battling Cancer. I was skin and bones. I would tell those that complimented me that I was sick and it was not healthy weight loss. I did not want people to look at my size with envy or admiration but wanted them to know it was an unhealthy way to loose weight and that I did not feel good at all.
    Thanks again for your posts. It makes me feel like I am not alone in my journey. I don’t have a lot of symptoms anymore and am at a healthy weight. However it is not completely gone. I am still working on it. Now that I know that diet does not cure it I eat a bigger variety of healthy foods with an occasional splurge. My mood is so much better!

    • Hi Michelle!! Thanks so much for sharing your story. I think it is amazing that you were able to let people know what was up when they complimented you on your weight loss! I wish I would have been able to do that more. I’m also glad to hear that you are tolerating more foods and gaining some weight back.

      You are definitely not alone and always welcome here at the SIBO diaries! Thanks for reading!

      • I relate to both of you so much. I get the same comments from my friends and the same worry from my family. I’m on such a restricted diet due to thinking I have candida and sibo but I think the real problem I need to be dealing with is my low stomach acid. Right now on this strict diet, I’m having the worst stomach pain I’ve ever had so I know something isn’t right. I also am suffering from low blood sugar now, low energy, too much weight loss, loss of menstrual cycle….and my docs don’t seem to care. Plus high anxiety / depression / mood swings. How did you go from such a strict diet to adding things back and getting healthier?

  • Initially one of my Doctors told me to start adding back some prebiotic foods. I immediately added onions and did not have any problems. Then I tested my tolerance for fructose by eating a small amount of mango the first day and progressively added more over 3 days. I did not have any symptoms so added in more fructose containing foods. Now I eat almost anything and just have some slight excessive burping or occasional chest bloating. I have gained back all of my weight, and unfortunately a few extra pounds. My BMs are normal probably 90% of the time. However I still have SIBO. I have gone through various treatments and still have it. In fact I just finished a 2 week treatment of Rifaximin and plan to do some herbals. I recently watched a you tube video by a Doctor and he said the most recent study shows that the best length of treatment with Rifaximin is 4weeks with some needing 8 to 12 weeks. Unfortunately my doctor did not prescribe me anything longer than 2 weeks. I do feel that the longer treatment would be beneficial for me so decided to continue with the herbals. I think so much of the treatment is trail and error which is such a bummer for the patient. Good luck with your treatment.

    • My biggest issue is that it doesn’t seem like any foods trigger any symptom. I ate a salad the other day (which I’ve eaten plenty of times) and have been severely bloated since. I think I need to focus more on the low stomach acid portion and less on the diet. I’ll have to trial and error things as well. But thank you! It helps to know others have gone through it and have gotten better. I’ve been on a candida diet for almost 5 months with little to no change (other than some rashes going away), and recently started low fodmap as well in the past month to see if it’d help some. Seems like neither are really helping and if anything making other issues worse….. this gives me hope though. Thanks!

      • I really could never pinpoint a specific food that caused my symptoms. It has been quite frustrating. However I do know that if I eat high fiber I definitely get symptoms. It is all so individual. I have read so many things about following a specific diet. I am not convinced that following any type of restrictive diet helps to get rid of the SIBO. I think the only thing the diet does is reduce symptoms. So if you are having a lot of symptoms I do think it helps. Some places I have read says you need to follow the diet to stave the SIBO but then other place I read say that it is impossible to starve SIBO. The bacteria will get their food somewhere and that somewhere is the mucosal lining of the gut. When they start eating that you will have more problems. I have also read that if you go really low carb then they adapt and learn to eat proteins and fats. I do not know who is right. It may be that no one is right it just depends on the person. That is what makes this so frustrating. Hang in there. I am much better and feel like SIBO is no longer controlling my life it is just part of my life. I really wish it were gone but it doesn’t really stop me anymore from enjoying life and that is what really matters.

    • Hi Michelle, can you please tell me what you did to overcome this? I lost so much weight also and I’m still stuck. Exactly what did you take ? thank you so much.

      • When I first got diagnosed my Hydrogen was 129 and I can’t remember what my Methane was. As a side I originally thought I had an bleeding ulcer and took two antibiotics for that. So my Hydrogen and Methane might have been even higher. I started on Oregano Oil and Berberine, 2 pills of each 3x/day. I was also taking a lot of supplements such as digestive enzymes ginger, licorice root, as well as Motilpro with 60 drops of Ibergast at bedtime. I also did a low FODMAP diet religiously. I was at a normal weight when this started and lost 17 pounds. I did all of this for 3 months. I also did a lot of yoga, tried visceral massage, manual treatments for a hiatal hernia (it was thought I had that as well), tried acupuncture, worked with a yoga therapist to work on my body and mood. After that my Hydrogen dropped to 49 and my Methane was lower but again don’t remember the number. I still had a lot of what I call chest bloating or trapped gas in my chest starting in the afternoon and getting worse in the evenings. I tried taking HCL with my meals. At first I thought it helped. I got up to 8 pills per meal. Then I started thinking it was making the chest bloating worse, however no burning or heartburn like symptoms. Then I took a round of Rifaximin by itself. Then I informed my Doc that I should have taken the Rifaximin with Neomycin due to the methane. I did another round of those together. Then my practitioner closed her practice. Then I saw Dr. Sanberg-Lewis, the Doc that started the SIBO clinic in Portland with Dr. Siebekker. He was the one who told me to start eating prebiotics. At that point I was kind of stuck for a year. I was doing a lot of self treatment with Atrantil, Prescript Assist probiotics, other supplements such as Butyrate, Tumeric, collagen, etc. special diet though eating healthy. I finally started to see a new Naturopath in my area. I did another breath test and it showed my Hydrogen at 79 and no Methane. It is normal for you Hydrogen to go up if you get rid of Methane as the Methane feed on the Hydrogen.She did a round of herbals with the SCD diet for one month. I did not feel any difference. I think around this time I started a new probiotic called Phage Complete developed by John Herron. The thing that is different about this probiotic is that is had phages in it. They are viruses that eat bacteria. I think that may have helped. Anyways, I recently did another round of Rifaximin with hydrolyzed guar gum, a biofilm disrupter, a probiotic, and ox bile for 2 weeks. This protocol is on Mona Mortenstien’s website. You can google her, she lives in Arizona. Rifaximin only works in the presence of bile, that is why it only works in the small intestine. Then after that I did a month of Candibactin AR and BR along with an elimination diet for 3 weeks. I just got back my last breath test and it is negative. So I got rid of my SIBO, but the one symptom that have wanted to get rid of, the chest bloating, is still there. So now, based on my research, I think I might have some yeast overgrowth as well. There is no definitive test for it but some practitioners do a stool test and I think a blood test. They also go by symptoms. My symptoms are very mild so it is hard to say. I might also just have a weakened LES from all of the bloating as well.

      • Hi Michelle, I really appreciate your reply and I will follow some of those suggestions. I wanted to know though, were you losing weight although you were eating ok or you lost weight because you weren’t eating. With me I kept losing weight while eating normal meals and that’s when I went to the doctor, they ran a bunch of tests including colonoscopy, endoscopy, many blood work and it was all normal. They did find mild gastritis , that’s it and I do have some muscle spasms also. I was so worried because I was losing while eating still so. So I was losing weight and feeling very drained as in energy was low and I always had my hand on my forehead from that odd feel. This was two years ago and I still feel the same to this day.