SIBO Causes Weight Loss | Here Why and How to Avoid 2023 Guide

SIBO Causes Weight Loss – Why and How to Avoid?

Patients that are SIBO positive may find managing their weight a monumental task. Some may experience a rapid weight loss of 20-25 pounds within a period of just 3-4 months.

Those that are affected by this scary weight loss will look and feel emaciated when they reach their lowest weight. What is more worrying is that not many nutritionists and health experts are aware of the fact that gut health plays a crucial role in managing your body’s weight.

Most people think that weight loss occurs due to eating disorders. Instead of finding the real cause behind your sickness, they will just advise you to eat high-calorie foods like cookies that will only make you sicker.

SIBO Leads To Weight Loss

We all know that SIBO is a condition that causes the accumulation of excessive bacteria in your small intestine. This bacterial overgrowth is frequently accompanied by malabsorption of food and chronic diarrhea. If you have SIBO, then you are also at risk of suffering from nutritional deficiencies, unintentional weight loss, and osteoporosis 1.

Many conventional doctors are not usually bothered by their patient’s severe weight loss. It seems that they ignore a person’s weight loss if his/her BMI falls within the normal range. Malnutrition is sometimes under-diagnosed in hospitals.

SIBO causes weight loss

Far too often, the lack of nutritional awareness among doctors causes malnutrition to go overlooked. However, an experienced functional practitioner or dietitian understands the severity of unintentional weight loss, and they quickly act when they see weight loss in SIBO patients.

Losing a significant amount of weight before or during treatment is a warning sign, which should not be ignored. If you are suffering from uncontrollably rapid weight loss, then you are either having issues with absorbing the food or not taking enough calories.

Why are SIBO Patients More Prone to Losing Weight?

  • The bacterial overgrowth disturbs the optimal digestive and absorptive ability, which often leads to a deficiency of vitamins and other nutrients. If you have SIBO, it does not matter what you eat. Even if you eat healthily, your body will probably not get the adequate amount of nutrients.
  • Symptoms like nausea, acid reflux, and fullness do not make it easy for SIBO patients to take food sources that are rich in calories.
  • SIBO sufferers are often prescribed overly restrictive diets, which is another reason why they suffer from malnutrition and rapid weight loss. When you have the same food every day, nothing sounds appetizing.
  • Excess bacteria in your gut interferes with the absorption of carbohydrates, and people who are SIBO positive are usually advised to avoid carbs to prevent diarrhea and bloating. Less carbohydrate intake means low energy and rapid weight loss.
  • If you are affected by bacterial overgrowth, then your gut is probably deficient in bile acids that are used for breaking down and absorbing fat. Malabsorption of fat produces different visible signs, such as oily stools and floating stools, with health effects such as fatigue and weight loss 2.

How to Determine that You are Rapidly Losing Weight

According to the American Dietetic Association, the weight loss criteria required for diagnosing malnutrition are 3:
  1. Equals or is greater than five percent weight loss in one month
  2. Equals or is greater than seven and a half percent weight loss in three months
  3. Equals or is greater than ten percent weight loss in six months
  4. Equals or is greater than twenty percent weight loss in twelve months

Most SIBO sufferers usually satisfy the criteria for the diagnosis of malnutrition. If you meet any of the above criteria, be sure to bring it to the notice of your healthcare practitioner or doctor. If they ignore your concerns, then find another doctor.

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What are the Consequences of Malnourishment in SIBO Sufferers?

Whether malnourishment occurs from poor absorption of nutrients or chronic under-eating, it is impossible to recover from small intestinal bacterial overgrowth (SIBO) if you are deprived of adequate amounts of nutrients. The consequences of chronic malnourishment and how it affects SIBO recovery are highlighted below:

1. Malnutrition has adverse effects on your body’s hormones

When you are underfed, your chronic stress response (HPA axis) gets activated, and the levels of cortisol start increasing. High levels of cortisol in the blood downregulate activation and synthesis of thyroid hormone, which gradually decreases your body’s metabolism.

When thyroid hormone activity is low, it becomes difficult to treat SIBO. Hypothyroidism, due to chronic stress activation along with malnutrition, slows down food motility through the gut. When motility is impaired, your small intestine becomes conducive to bacterial overgrowth.

SIBO causes weight loss

Moreover, HPA activation creates a SIBO-friendly environment by lessening blood flow, nutrients, and enzymatic release to the stomach, impairing digestion, thereby weakening your gut barrier function. As a result, chronic stress activation caused by malnutrition wreaks havoc on your gut.

Sex hormones also decrease if your body fat becomes significantly low. As you lose fat, leptin level drops, and it signals your brain that the energy stored is low. Since the process of reproduction perhaps requires maximum energy, the brain suppresses the synthesis of sex hormones when the leptin level is too low.

2. Deficiency of nutrients prevents healing

The lesser the nutrients and calories you are absorbing or consuming, the more the chances that you are not meeting the nutritional requirements of your body. Bacterial overgrowth reduces the absorptive ability of your gut, and when it is accompanied by a restrictive diet, your body’s nutrient status gets walloped.

Without enough calories, your body will not get the fuel for proper immune function, energy metabolism, GI tract repair, and hormone function.

SIBO causes weight loss

Carbohydrates are useful for RBCs and brain cells, as well as for supporting hormone functions and preventing proteins from getting broken down into glucose. Eating plenty of proteins is also necessary for repairing and maintaining the intestinal barrier, as well as to sustain muscle mass.

While adequate amounts of micronutrients are needed for healthy gut function, these are also essential for healing from SIBO. Nutrients like zinc, choline, selenium, vitamin C, glycine, omega three fatty acids, and glutamine are required for the formation of IgA antibodies.

How to Diagnose Why You are Losing Weight?

If you are not able to maintain a healthy weight, then you should try to identify whether the weight loss is due to undereating or poor absorption. First, you must rule out the deficiencies in absorption.

The cheapest and easiest way to identify it is by checking your stool. If you find undigested food objects in your stool or oily and pale poop, then you are suffering from malabsorption. Floating stools that are harder to flush also indicate poor absorption.

You can undergo a comprehensive stool analysis, which will give you a clear picture of your gut’s absorption capacity 4. Levels of protein breakdown products and fecal fat found in your stool show whether you are absorbing well.

For confirming that you are undereating, you need to track your daily calorie intake for 3-7 days to have an idea about the average amount of calories you are eating. You can use an online calorie calculator to compare your daily calorie intake with your estimated calorie requirement.

How to Deal with Weight Loss Caused by SIBO

  1. Limit hard-to-digest carbs that fuel SIBO: Bacterial overgrowth that produces proteolytic enzymes and toxins can damage the delicate structures of the small intestine. By controlling the overgrowth, you can restore your stomach’s lining and reduce malabsorption.
  2. Increasing dietary fats: People who cannot maintain their weight tend to have a lesser amount of fat in their diet. Moreover, dietary fats help in restoring lost calories when the carbohydrates are restricted.
  3. Including easy-to-digest carbohydrates: These carbs have a lesser chance of being poorly absorbed and are less likely to cause SIBO.
  4. Finding and addressing the factors that may contribute to malabsorption and promote SIBO: Several underlying factors can be dealt with by simply having dietary supplements. For example, if you are not tolerant to lactose, you can control it by avoiding high-lactose dairy products and taking lactose enzyme. Check out our SIBO Elimination Toolkit to know more about factors that promote SIBO and how to treat them properly.


Malnutrition caused by under-eating or malabsorption during SIBO treatment can spoil your chances of SIBO recovery. If your body is deprived of essential macronutrients, you will not be able to heal from SIBO.

Losing one or two pounds of weight is not a matter of concern, but experiencing a severe unintentional weight loss means that you should consult a medical professional or dietitian to regain the weight.

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