Understanding the Gut-Brain Connection in Eating Disorders: More Than Just a Gut Feeling

By Sam Coates and Georgia Spence

We’ve all heard the phrase ‘gut feeling’, haven’t we? Turns out, it’s not just an old wives’ tale! It hints at something many nutrition professionals see the impact of daily!

Our gut isn't just simply responsible for facilitating the absorption of nutrients; it also hosts the complex Enteric Nervous System (ENS), often dubbed the 'second brain'.  This system is in constant dialogue with the Central Nervous System (CNS) via the gut-brain axis (Carabotti et al., 2015). Think of it as a biological superhighway using neural signals (like the vagus nerve), hormones, and immune messages to chat back and forth. Like with any relationship, communication, instructions and information do not just flow one way, in fact out gut not only  influences digestion; but also has powerful impacts on mood, reward systems, and overall health (Carabotti et al., 2015).   

Now, throw an eating disorder (ED) into the mix…

Behaviours we frequently encounter, such as dietary restriction, binge-purge cycles, chaotic or restrictive eating patterns, can significantly interfere this vital communication highway.

Therefore, it makes sense that so many of our patients report persistent and distressing gut symptoms – bloating, pain, constipation, diarrhoea, lack of hunger signals and / or  feeling full after only a few bites (early satiety).

These symptoms can hang around even when nutritional rehabilitation and weight restoration (Sato and Fukudo, 2015).

Getting our heads around the mechanisms driving these symptoms isn't just academically interesting; it's crucial for supporting our patients holistically and improving their chances of achieving sustained recovery.

Key Factors interfering with the Gut-Brain Axis in ED’s:

Several interconnected factors could be contributing to the gut disorders and psychological distress we see within this patient group:

Altered Gut Microbiota (The Bug Balance): Our guts are full of microbes that are essential for digestion, nutrient absorption, immune function, and even making neurotransmitters (Thursby and Juge, 2017). ED behaviours can drastically disrupt this internal ecosystem – altering its composition and reducing its diversity. For example, severe dietary restriction often results in a reduction in quantity and variety of fibre being consumed, and therefore reaching the gut to feed these microbes. In effect, the beneficial bacteria are starved, and therefore reduce in number, causing an imbalance between different microbes (Mack et al., 2016).

Changes in Gut Motility (How Things Move): When energy is restricted or its consumption is unpredictable, the coordinated muscle contractions pushing food along can become sluggish or erratic. In addition long term malnutrition can result in the weakening of gut muscles, alongside hormonal changes which in turn disrupt the messages  controlling peristalsis (Norris et al., 2016). Clinically, this often manifests as constipation,  gastroparesis or delayed stomach emptying, culminating in that familiar early satiety and discomfort after eating. (Salvioli et al., 2007; Norris et al., 2016).

Heightened Visceral Sensitivity (Feeling Too Much): This means an increased perception of pain or discomfort from internal organs, even from normal digestive processes like gas movement or stomach stretching (Van Oudenhove et al., 2011). For most people, when food is moving through their gut they are none the wiser, but for someone with increased visceral sensitivity they can feel so much more, from the contraction of the gut muscles to the natural stretching of the stomach to accommodate a meal.  The exact 'why' is complex, involving sensitised nerve pathways between the gut and brain. When studies within the context of IBS have investigated this, it appears this  can be fuelled by psychological distress (such as anxiety) and changes in neurotransmitter signalling due to a disrupted gut microbiome (Kennedy et al., 2012). When normal sensations are amplified and felt as pain, it can significantly contribute to the fear of eating and drive persistent avoidance - just as many of us see when working with our clients.

The Vicious Cycle.

Like the majority of things within the human body, it is all connected, often creating a challenging cycle. 

Inconsistent or restricted intake leads to dysbiosis, worsening bloating and pain (Mack et al., 2016). 

Malnutrition is thought to impair the body's ability to make vital neurotransmitters.

Then add stress and anxiety – often companions in EDs. The body’s stress response system releases cortisol which slows digestion, over the long term can alter the microbiome, and even increase visceral pain sensitivity (Konturek et al., 2011; Qin et al., 2014).

As a result, pursuing a ‘normal’  eating pattern and managing food-related anxiety just got even harder…

Gut symptoms fuel the anxiety about eating, anticipating discomfort, whilst the resulting dysbiosis from restriction and inconsistent eating patterns fuels further changes in gut motility, visceral sensitivity and neurotransmitter production, which in turn directly impacts mood and increases anxiety….and round and round the cycle goes (Sato and Fukudo, 2015).   

What can we do about it?  Healing the Gut and Mind Together

Breaking this cycle through the lens of the gut brain axis is essential for successful ED recovery. Persistent gut symptoms are a major hurdle to nutritional rehabilitation, increase relapse risk, and severely impact quality of life (Sato and Fukudo, 2015). Effective management demands a multidisciplinary approach, blending nutritional therapy with psychological support.

Want to learn more? Our upcoming study day is designed precisely to equip you, as healthcare professionals, with the knowledge and practical tools to support patients navigating these complex gut-brain challenges. We'll explore diagnostic approaches and evidence-based interventions, looking at how to these integrate strategies into your practice!

References

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