Have You Ever Had a Gut Feeling? The Gut–Brain Axis and Eating Disorders: Understanding Digestive Symptoms in Recovery

We often talk about “gut feelings”. What if this expression is more literal than we realise?

What can the Gut–Brain Axis Tell Us About Eating Disorders

Many people living with eating disorders experience digestive symptoms such as bloating, constipation, stomach pain or reflux. In clinic, digestive symptoms are one of the most common concerns patients raise; sometimes even before they talk about food or weight.

These symptoms are often dismissed as “just part of recovery.” But research increasingly shows that something deeper may be happening.

The digestive system and the brain are closely connected through a communication network known as the gut–brain axis. Understanding this connection can help explain why digestive symptoms and mental health often influence each other so strongly. In other words, the gut is not simply digesting food; it is constantly in conversation with the brain.

What Is the Gut–Brain Axis?

The gut–brain axis refers to the constant communication between our digestive system and our brain.

This communication occurs through several pathways:

• the vagus nerve, which directly links the gut and brain

• hormonal signalling

• the immune system

• the gut microbiome i.e., the trillions of microorganisms living in the digestive tract

Because of this network, digestion can influence mood and behaviour, while stress and emotional distress can directly affect digestion.

This is why anxiety often shows up first as a physical sensation in our stomach.

The Gut Microbiome: A Hidden Ecosystem

Inside the digestive system lives a vast ecosystem known as the gut microbiome.

The human gut contains around 100 trillion microorganisms, forming a complex community that supports many essential functions in the body.

These microbes help regulate:

• digestion and nutrient absorption

• immune function

• metabolism

• the production of neurotransmitters involved in mood

For this reason, the microbiome is increasingly recognised as an important contributor to both physical and mental health. 

When the Gut Microbiome Becomes Imbalanced

A healthy microbiome is sometimes referred to as eubiosis, meaning a balanced and diverse microbial environment.

In contrast, dysbiosis describes an imbalance in gut bacteria. This can lead to:

• increased intestinal permeability, i.e., leaky gut

• higher levels of inflammation

• worsening digestive symptoms

• disruption of communication along the gut–brain axis

Dysbiosis has been associated with several conditions, including gastrointestinal disorders and mental health difficulties.

How Eating Disorders Affect Gut Health

Eating disorders can significantly alter the gut environment.

Periods of undernutrition or starvation may change the composition of gut bacteria and reduce the production of beneficial compounds that support gut health.

At the same time, neurotransmitters that regulate mood also influence digestion.

For example:

• Serotonin, often associated with mood, also regulates intestinal movement

• Dopamine, involved in reward pathways, influences motivation and cravings

Research in anorexia nervosa suggests that although microbiome diversity often improves during nutritional rehabilitation, digestive symptoms may persist during recovery. This may partly explain the reason that bloating, discomfort or constipation can continue even after eating patterns become more regular.

Behaviours That Can Further Disrupt Gut Function

Certain behaviours associated with eating disorders can worsen digestive symptoms.

For example, laxative misuse may lead to complications such as: electrolyte imbalances, dehydration, alternating diarrhoea and constipation and in severe cases, cardiac complications. Importantly, the weight changes people notice from laxatives are usually related to fluid shifts rather than fat loss, yet the behaviour can still cause serious medical harm.

Supporting Gut Health During Recovery

Although research into the microbiome and eating disorders is still evolving, several factors are known to support gut health.

Nutrition

Foods that support microbial diversity include:

• fibre-rich foods (e.g., whole grain carbohydrates, lentils, chickpeas, beans, chia seeds, flaxseeds, nuts, sweet potatoes etc)

• fruits and vegetables rich in polyphenols (e.g., berries, apples, grapes, pomegranate, spinach, kale, onions, dark chocolate, green tea etc)

• fermented foods (e.g., yoghurt, kefir, sauerkraut, kimchi, miso, tempeh)

• omega-3 fatty acids (e.g., walnuts, flaxseeds, chia seeds, hemp seeds, algae-based omega-3 supplements)

• foods containing tryptophan (e.g., eggs, poultry, cheese, yogurt, tofu, pumpkin seeds, sesame seeds, oats)

These nutrients support both digestive health and brain function.

Psychological Support

Because the gut and brain communicate in both directions, psychological approaches can also influence digestive symptoms. Approaches such as psychotherapy, gut-directed hypnotherapy and/or relaxation and breathing techniques may help regulate the stress response and support gut functioning.

Probiotics and Related Supplements

You may have heard of:

• probiotics: live microorganisms that may provide health benefits

• prebiotics: fibres that feed beneficial gut bacteria

• synbiotics: supplements that combine both

• Researchers are also exploring psychobiotics, which are probiotics that may influence mental health.

However, evidence is still developing and there is no single probiotic that works for all digestive symptoms, so supplementation should ideally be considered with professional guidance.

What Makes This Connection Important

The gut–brain axis reminds us that eating disorders affect far more than food intake or body weight. They influence complex biological systems that connect digestion, metabolism, mood and behaviour.

For many people, digestive symptoms are not simply side effects of the illness, they are part of the body’s broader physiological response to stress and disrupted nutrition. Understanding this connection can help people make sense of their symptoms and highlights why both nutritional and psychological support are essential in recovery.

The gut–brain axis is a growing area of research, but it already helps explain something many people in recovery recognise: when the gut struggles, the mind often feels it too.

References

1.     Zipfel S., Giel K., Bulik C., Hay P., Schmidt U. (2015). Anorexia nervosa: aetiology, assessment and treatment. The Lancet, 395(10227), 899–911.

2.     Cryan J.F., Dinan T.G. (2012). Mind-altering microorganisms: the impact of the gut microbiota on brain and behaviour. Nature Reviews Neuroscience, 13, 701–712.

3.     Mack I. et al. (2016). Weight gain in anorexia nervosa does not normalize gut microbiota composition. Nature Microbiology, 1, 16058.

4.     Mayer E.A., Knight R., Mazmanian S.K., Cryan J.F., Tillisch K. (2014). Gut microbes and the brain: paradigm shift in neuroscience. Journal of Neuroscience, 34(46), 15490–15496.