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August 18, 2023

98% of People With Eating Disorders Have A Gut Disorder - Here’s Why Cutting Out Gluten and Dairy Might Make Gut Health Worse


If I had a dollar for every time I saw a “gut health coach” (what is that?) say that you should cut dairy and gluten if you want to improve your gut health. “Gut health” in itself is a misnomer, not really referring to anything medically testifiable, but we’ll accept it as a slang term for the sake of this discussion.

Back to improving gut health - will cutting out food groups help to heal your gut? Combat bloating? Make your bowel habits more regular. The short answer is no. Unless you have a disorder like celiac disease, cutting out food groups will cause more harm than good. In fact, you might worsen bloating, constipation, stomach pain, and other symptoms of gut dysbiosis.

In 2019, I graduated with a Master’s degree in Nutrition. For the entire year, I focused my research on gut health, conducting a thesis on why there’s such a strong link between disordered eating habits and gut problems.

I summarized everything I learned in this research project into a book, “Gut Healthy, Mind Happy,” which is now available on Amazon. Check it out.


A study found that 98 percent of females with a documented eating disorder also fit the criteria for a functional gut disorder, and 50 percent met the criteria for IBS. So what is the connection between disordered eating and gut problems? This question is what drove me to conduct my master’s thesis on gut health and disordered eating. Here are some of the key insights.

What is disordered eating?

Eating disorders are relatively rare, affecting approximately nine percent of the population. Under the bracket of eating disorders lies anorexia nervosa, bulimia nervosa, and binge eating disorder. However, broader definitions of eating disorders, including avoidant/restrictive food intake disorder (ARFID), diabulimia, compulsive exercise, and orthorexia, increase the total rates of disordered eating significantly to a widespread condition.

Yet no comprehensive study has yet been able to establish the exact percentage of the population affected because some of the broader conditions are largely undiagnosed. 

Disordered eating disproportionately affects women, with the most extensive study finding that of all cases, approximately 25 percent are men and 75 percent are women.

The connection between disordered eating and poor gut health

The correlation between disordered eating and IBS is significant. Not only is the prevalence higher amongst women in both conditions, but researchers have also suggested that one disorder may precede, or at the least exacerbate, the other, partly due to the gut-brain connection.

A study that used participants who have, or have had, an eating disorder found that 64 percent currently met the criteria for IBS, with 87 percent of participants developing an eating disorder before developing IBS.

People with disordered eating typically have fewer microbes and different types of microbes in their gut compared to healthy individuals. Another study found that 44.4 percent of people who have GI disorders have disordered eating habits, a significantly higher percentage than in a healthy population.

Does poor gut health cause disordered eating or the other way around? It depends. But the research shows that one often comes before the other. Here are some of the features of disordered eating that harm gut health.

Irregular eating 

Surprisingly, your gut microbes are affected by your eating habits - not just what you eat but also when you eat. Studies have found that eating regularly increases microbial abundance, whereas disordered eating habits reduce healthy gut bacteria. That’s in part why there is a correlation between people with disordered eating and digestive issues.

Our gut microbiota can rapidly respond to dietary changes, perhaps based on our volatile hunter-gatherer diets, which were characterized by periods of feast and famine. Going through long, sudden periods without food required our bodies to adapt. But that doesn’t mean the adaptation is necessarily beneficial. For people experiencing gut problems, it’s better to eat regularly to keep their body and bacteria nourished so they can function optimally.

Restrictive eating

There are a few key mechanisms to understand when examining how restrictive eating can harm gut health. First, eating a restrictive diet limits the variety of bacteria in your gut microbiome. A restricted diet can also cause nutrient deficiencies, which harm digestive function. 

A study found that people with IBS were more likely to avoid eating even when hungry (43 percent), vomit after eating (13.6 percent), reduce daily intake of calories, and cut out dairy compared to a control group. The study concluded by saying people with IBS are more likely to engage in detrimental eating habits and behaviors.

Altered eating habits such as in the case of disordered eating often may include restriction of certain food groups, a reduced total intake of food, purging, compulsive exercise, and other traits that can disturb the homeostasis in the body and mind. It is still unclear as to whether an imbalance in the gut microbiome promotes this behavior change or whether these behaviors in fact cause an imbalance in the gut.

As one example, the act of purging (forcibly throwing up) is a component of bulimia nervosa and can present in other types of disordered eating. It causes acid reflux and the parotid glands to become swollen. The sphincter that controls the stomach and esophagus becomes weaker, allowing partially digested food and stomach acid back from the stomach to the esophagus and throat. This causes inflammation in the stomach lining, causing bloating, indigestion, lack of nutrient absorption, gas, and constipation. These symptoms mirror a GI disorder but are entirely caused by eating behaviors.

But in some cases, this chronology is reversed.

Experiencing gut problems may cause someone to cut out food groups in an attempt to control their symptoms. But this is a bad idea. A clinical trial found that chronic food restriction promotes intolerances to foods that were previously tolerated due to the decrease in digestive enzyme production. This can lead to, or exacerbate, gut-related problems.

Restriction of food groups or intake for an extended period of time also changes the gut microbiota. A study looked at what happened when individuals without a gluten allergy (celiac) ate a gluten-free diet. The researchers found that after one month, their healthy gut bacteria decreased, unhealthy bacteria increased and participants experienced reduced immune function.

Overall, eating disorders can harm gut health by causing nutrient deficiencies, altering gut hormone signaling, damaging the gut lining, and dysregulating the gut microbiome. 

Negative thoughts surrounding food

Disordered eating and IBS often present with psychological conditions like depression and anxiety. The gut-brain axis may be responsible for the underlying psychological component of both of these conditions, with research linking both disorders to imbalances in the gut microbiome. 

Nutritional psychology is the correlation between what you eat and how you think. You’re probably aware that what you eat affects your body and mind in terms of the nutrients it provides. But what if I told you that the way you think about your food also affects you beyond the nutritional composition of the food? This isn’t a “woo-woo” branch of mysticism, it has been proven in randomized controlled trials!

To clarify, our thoughts can’t change the nutritional composition of the food. An apple will always be an apple, even if you think hard about it being a banana. However, our thoughts can alter our metabolic processes. How we think about our food affects our internal neurobiology and nervous system.

When we view a plate of food, it takes shape in the cerebral cortex. This cognitive process then interacts with the limbic system, where emotions and primary motivational drives are born. The hypothalamus and the insula are responsible for processing the information surrounding the food and the emotional response to it. For example, if the plate of food in front of us is something we deem healthy and delicious, the hypothalamus modulates this positive message through the activation of the parasympathetic system, which stimulates digestion and activates metabolism. This means you’ll digest the food properly, and the maximum amount of nutrients will be absorbed.

On the flip side, if you feel guilty and disgusted with yourself for eating a plate of food, the negative emotions will signal the sympathetic nervous system (SNS). This exerts an inhibitory effect upon digestion by inhibiting gastrointestinal motility, mucosal secretion, and blow flow. This slows down digestion, which has a negative effect on the gut microbiome. First, it alters the gut microbiota, and second, it increases toxic waste products that should have been excreted more rapidly. When your SNS is activated, insulin and cortisol are spiked, which also affects how your food is metabolized, resulting in more stored fat.

In essence - triggering the SNS prevents your gut from doing its job, and you’re more likely to experience gastrointestinal disturbances like bloating, stomach pain, and constipation. From your thoughts alone! Remember, your gut is your second brain. The way you think about the food you eat makes a huge difference.

Some researchers wanted to test this. They put a milkshake into two separate packages - one that advertised it as a low-calorie drink called Sensishake - advertised as having zero percent fat, zero added sugar, and only 140 calories. The other packaging was labeled as Indulgence - with 620 calories, saturated fat, and sugar. In reality, both shakes were the same, each containing 300 calories.

The research participants both drank their shakes, and the researchers measured their levels of ghrelin. Ghrelin is a hormone secreted in the gut, known as the “hunger hormone”. When ghrelin levels rise, it’s your body’s way of signaling that it’s hungry and needs to eat. When you eat a big meal, and you’re satiated - ghrelin drops. As an evolutionary adaptation, when ghrelin levels rise, your metabolism slows. This is to account for the times that you may not immediately find food and need to conserve energy. 

You may assume that hormones like this are controlled by the amount of energy and nutrients the food contains - your gut can’t see the food, right? So surely the nutritional composition of the food is the only factor that matters. That’s not what the researchers found.

The people who drank the calorie-dense shake Indulgence experienced a three times higher drop in ghrelin compared to the group who drank what they perceived to be a low-calorie shake. The people who drank Indulgence believed they were getting more calories, and so their guts responded to this belief. Does that mean you can eat whatever you want as long as you tell yourself it’s healthy and low-calorie? No. The nutritional composition of your food still matters. But we can’t ignore the effect our thoughts and feelings have on our digestion, biology, and hormones. 

Stress and negative feelings about food prevent you from digesting it properly. You get more benefits from your food when you eat it with positivity and good thoughts. Some say it’s the placebo effect. But does it matter if it is a placebo if it still works? Food isn’t the enemy. In fact, it’s your life force!

Final words

The connection between disordered eating and gut problems is undeniable. Studies have shown that a significant percentage of individuals with eating disorders also experience functional gut disorders, such as IBS.

The gut-brain connection plays a crucial role in this relationship, with one disorder often exacerbating or preceding the other.

Disordered eating habits, including irregular eating patterns and restrictive diets, can harm gut health by reducing healthy gut bacteria, causing nutrient deficiencies, and damaging the gut lining; while negative thoughts and emotions surrounding food also impact digestion and metabolism, leading to gastrointestinal disturbances.

It's important to recognize the impact of both nutritional composition and our thoughts and feelings on our gut health. Nourishing our bodies with a positive mindset and a balanced diet can promote optimal digestion and overall well-being.

Remember, food is not the enemy. Let us embrace a holistic approach to healing, focusing on both our gut and our mind for a healthier and happier life.

Want to learn more about gut health and how to treat gut problems using science? Click here to read my book.


Hello, I'm Emilina

Welcome to my content hub. I'm a health writer, published author, nutritionist, and personal trainer. If you're interested in working with me or would like to discuss a project, please click the links below.


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