The Overlap Between Eating Disorders and Gut Disorders: A Complex Relationship

By Sam Coates and Georgia Spence

We've all seen it in practice: an eating disorder patient reporting severe abdominal pains, bloating, nausea and constipation, sharing that the symptoms only worsen when they eat, and don’t seem to be getting easier.

For a long time, these troubles were largely viewed as an expected, secondary consequence of the ED itself. - But is that really true?

The short answer is NO - Emerging research suggests the link between GI issues and Eating Disorders (ED’s) is far more complex than once thought.

New research points to an intricate, bi-directional relationship between EDs and functional

gastrointestinal disorders (FGIDs) – think conditions like irritable bowel syndrome (IBS) and

functional dyspepsia, where the gut misbehaves without obvious structural damage (Sato and Fukudo,2015).

This complex interaction forces us to ask some key questions…

Could underlying gut issues have contributed to an individuals development of persistence of an ED or disordered eating?

Or is it the other way around… is the physiological toll of weight restoration and more regular eating patterns, alongside the psychological toll of recovery driving gut dysfunction?

Whilst this can feel a bit like a ‘chicken and egg’ situation, getting clear on this overlap is essential for effective treatment planning and supporting patients to make meaningful steps to long term recovery.

Just How Common is this Overlap?

To put it bluntly: VERY

The link between EDs and GI symptoms is incredibly strong. Clinical studies consistently show a huge majority of individuals with EDs experience significant gut distress. For instance, research looking at patients in inpatient units found functional GI symptoms reported by 98% (Boyd, 2005)! Common complaints included: bloating, constipation, diarrhoea, nausea, abdominal pain, early satiety and reflux (Sato and Fukudo, 2015; Riedlinger et al., 2021).

Crucially, these aren't just fleeting issues tied to the acute phase of illness. Many individuals find these gut problems persist even after nutritional rehabilitation and weight restoration. As you can imagine, individuals suffering with IBS even without the comorbid eating disorders, the persistence of these gut issues have major impacts on long-term quality of life, relationships with food and, in the context of a ED, can increase risk of relapse (Boyd et al., 2017). The persistence of these uncomfortable sensations can understandably fuel food avoidance, heighten anxiety around meals, and reinforce restrictive or other disordered eating patterns – a cycle many clinicians will recognise.

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The Science: So, how exactly do EDs exert such a profound impact on the digestive system?

Several mechanisms are at play:

1. Malnutrition and Restriction: When energy and nutrient intake are inadequate (characteristic of disorders like anorexia nervosa), there is insufficient energy in the system for bodily functions including peristalsis to occur. As a result, gut motility often slows right down, in some cases this can lead to slow gastric emptying, constipation or even gastroparesis. Additionally, the body may also produce fewer digestive enzymes and struggle with nutrient absorption (Norris et al., 2016). This further contributes to symptoms like constipation, bloating, and that frustrating early fullness.

2. Consequences of Purging Behaviours: Self-induced vomiting (seen in bulimia nervosa and

AN-binge/purge subtype) can lead to oesophagitis, dental erosion, and electrolyte

imbalances that disrupt gut muscle function. Meanwhile, laxative abuse throws normal

bowel function completely out of sync, potentially leading to dependence and long-term

issues (Mascolo et al., 2020).

3. Effects of Binge Eating: Consuming very large quantities of food rapidly can simply

overwhelm the digestive system's capacity, causing acute bloating, pain, and distension

(Latorre et al., 2023).

4. Gut Microbiota Alterations: Both malnutrition and erratic eating patterns can significantly

alter the composition and diversity of the gut microbiome. This dysbiosis is thought to

potentially contribute to gut inflammation and interfere with gut-brain communication

pathways (Mack et al., 2016; Ruusunen et al., 2019), which in turn can fuel feelings of

anxiety.

The Other Side of the Coin: How Gut Disorders Can Influence Eating Behaviours

It’s not just a one-way street. Pre-existing or co-occurring FGIDs can significantly influence eating behaviours and potentially contribute to the development or maintenance of EDs:

1. Symptom-Triggered Food Avoidance: Patients with conditions like IBS or functional

dyspepsia often associate certain foods, or even the act of eating itself, with unpleasant

symptoms like pain, bloating, or diarrhoea. This can understandably foster a fear of eating

and lead to increasingly restrictive diets in an attempt to manage symptoms (Zia et al.,

2016). While intended to help, severe restriction risks nutrient deficiencies, weight loss, and

can cultivate an unhealthy preoccupation with food – blurring the lines with ED

psychopathology.

2. Heightened Interoceptive Awareness: Individuals with FGIDs frequently experience

heightened sensitivity to internal bodily sensations – known as visceral hypersensitivity. This intense focus on gut feelings can exacerbate anxiety around food and eating, potentially contributing to disordered patterns (Boyd et al., 2017).

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3. Diagnostic Overlap and Challenges: Clinically, the symptoms of FGIDs can sometimes mimic or significantly overlap with ED presentations. This is particularly true for

Avoidant/Restrictive Food Intake Disorder (ARFID), where food intake is limited due to

sensory sensitivities, fear of aversive consequences (like choking or vomiting), or an

apparent lack of interest in food (Zimmerman & Fisher, 2017). Differentiating between an FGID driving restrictive eating versus an ED causing GI symptoms requires careful, nuanced assessment.

The Gut-Brain Axis: The Crucial Communication Highway Central to this whole interplay is the gut-brain axis – the constant, bidirectional communication superhighway links the central nervous system with the gut's own intrinsic nervous system (the enteric nervous system). This isn't just vague wiring; it involves specific neural pathways (like the vagus nerve), hormonal signals (like cortisol and gut peptides), immune mediators (like cytokines) and, critically, the gut microbiota (Cryan et al., 2019).

Psychological factors so prevalent in EDs – high stress levels, anxiety, depression, trauma history – can also directly impact gut function via this axis, altering motility, secretion, and visceral sensitivity (Konturek et al., 2011). Conversely, disturbances originating in the gut – inflammation, altered motility, dysbiosis – send signals up to the brain that influence mood, increasing anxiety, effecting appetite regulation, and even cognitive function (Cryan et al., 2019; Mack et al., 2016).

As you can imagine, this creates the perfect storm for a vicious cycle: gut symptoms worsen

psychological distress, which in turn exacerbates gut symptoms, potentially perpetuating the

disordered eating behaviours we are trying to treat.

Implications for Treatment: Supporting patients from Head to Gut.

This significant overlap demands an integrated approach to care and as nutrition professionals often ensures the need for a more specialised nutrition plan that not only seeks to overcome restrictive patterns, but also considers the importance of supporting the gut microbiota through regular and varied nutrition

Where to Start - Learn More and Enhance Your Practice

Navigating the complexities of co-occurring gut and eating disorders presents unique challenges for clinicians.

If you're looking to gain deeper insights and practical tools to manage this overlap effectively, consider joining our upcoming study day: Management of Gut Disorders in Disordered Eating and Eating Disorders. Designed specifically for healthcare professionals working within ED services, this event (held across two half days) will provide evidence-based knowledge and clinical strategies. Our goal is to equip you to better understand the mechanisms at play and implement tailored interventions that address

both the gut and the mind, ultimately improving outcomes and quality of life for the individuals we work with.

Join us on the 9th and 10th of June for our upcoming study day

References

Boyd, C., Abraham, S. & Kellow, J. (2005) Psychological features are important predictors of

functional gastrointestinal disorders in patients with eating disorders. Scandinavian Journal of

Gastroenterology, 40(8), pp. 929-935.

Boyd, C., Abraham, S. & Kellow, J.E. (2017) Appearance and disappearance of functional

gastrointestinal disorders in patients with eating disorders. Neurogastroenterology & Motility,

29(10), e13101.

Cryan, J.F., O'Riordan, K.J., Cowan, C.S.M., Sandhu, K.V., Bastiaanssen, T.F.S., Boehme, M.,

Codagnone, M.G., Cussotto, S., Fulling, C., Golubeva, A.V., Guzzetta, K.E., Jaggar, M., Long-Smith,

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O'Connor, R., O'Mahony, S., O'Neill, I., Palamara, I., Perez-Pardo, P., Prescott, S.L., Stanton, C.,

Clarke, G. & Dinan, T.G. (2019) The Microbiota-Gut-Brain Axis. Physiological Reviews, 99(4), pp.

1877-2013.

Konturek, P.C., Brzozowski, T. & Konturek, S.J. (2011) Stress and the gut: pathophysiology, clinical

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Latorre, R., Stern, E., Hujoel, I.H. & Fass, R. (2023) The Interplay Between Eating Disorders and

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Mack, I., Cuntz, U., Grämer, C., Niedermaier, S., Pohl, C., Schwiertz, A., Zimmermann, K., Zipfel, S.,

Enck, P. & Penders, J. (2016) Weight gain alters the gut microbiota in patients with anorexia nervosa.

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Cremon, C., Stanghellini, V. & Bellini, M. (2020) Functional Gastrointestinal Disorders in Eating

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