Feeling tired all the time? You’re not alone. Many of us are getting enough sleep and  staying active yet still struggle with low energy, brain fog, or feeling off. In recent years, more people have started asking whether their gut health could be part of the problem.

Sometimes it is. Your gut microbiome, the trillions of bacteria living in your digestive system, can affect inflammation, nutrient absorption, stress hormones, and even communication between your gut and brain. While gut issues are not the only cause of fatigue, they may play an important role in some people.

Here’s what research says about gut health and fatigue, what the microbiome may actually influence, and practical steps that may help support better energy levels.

Can poor gut health cause fatigue?

While the gut is central to immune function and nutrient metabolism, it should be viewed as one component of a complex biological system. Rather than being a single cause of general fatigue, the gut microbiome often serves as a critical mediator of many physical and lifestyle factors that affect our daily energy levels.

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Factors that impact your energy

Factor	Gut microbiome’s role	What this means
Sleep	Contributes to sleep and wake cycles through signals between the gut and the brain [1]	Some gut bacteria help make chemicals like serotonin and GABA that support sleep and relaxation
Diet & nutrition	Helps break down food and helps the body absorb nutrients [2]	Gut bacteria help digest food and release nutrients your body needs. For example, they help break down fiber and make helpful compounds called short-chain fatty acids
Physical activity	Helps the body use energy and adjust to exercise [3]	Gut bacteria may help your body use energy better during exercise. For example, they may affect how muscles use sugar and fat for fuel
Stress & mental health	Helps control how the body reacts to stress through the gut-brain connection [4]	Gut bacteria may affect how stressed you feel. For example, they can influence cortisol, a hormone your body makes during stress
Hormones	Helps control how the body uses and breaks down hormones [5], [6]	Gut bacteria can affect hormones that control your body. For example, they can influence insulin and thyroid hormones
Body composition	Affects how the body stores fat and uses energy [5]	Gut bacteria can influence weight and energy use. For example, they can affect how the body stores fat and responds to insulin
Lifestyle habits	Changes based on daily habits like diet, sleep, and alcohol intake	Your daily habits can change your gut bacteria. For example, alcohol can reduce helpful bacteria and affect how your body makes energy

Beyond these broader influences, a specific topic that often arises in conversations about chronic tiredness is the concept of intestinal permeability, or "leaky gut."

Can “leaky gut” cause fatigue? What the research shows

Many people searching for answers about fatigue and leaky gut wonder whether intestinal permeability directly causes tiredness.

The research is still evolving. Most studies have focused on people with Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS), and have found higher markers of intestinal permeability and inflammation [7],[8]. However, scientists have not proven direct causation.

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Claim	What studies actually show	Bottom line
“Leaky gut directly causes chronic fatigue”	Some ME/CFS studies show higher inflammatory and permeability markers [7], [8]	Possible contributor, not proven cause
“Intestinal permeability triggers brain fog”	Bacterial lipopolysaccharide (LPS) that slips through the gut barrier can activate brain inflammation in animal models [9]	Human evidence is limited
“Fixing leaky gut restores energy quickly”	Repairing the gut lining may support overall health, but fatigue often has multiple causes [10]	Improvements may take time
“Zonulin tests diagnose leaky gut”	Zonulin testing remains controversial and is not fully standardized [11]	Results should be interpreted carefully

Current evidence supports the idea that intestinal permeability may play a role in inflammation and fatigue for some individuals, especially after infections or chronic stress. But fatigue is complex and rarely has a single cause.

Adrenal fatigue and gut health: untangling the buzzword

“Adrenal fatigue” is a popular term online, but it’s not recognized as a medical diagnosis by major endocrine organizations [12]. Despite this, symptoms of chronic stress, such as fatigue, anxiety, brain fog, and salt or sugar cravings, are often attributed to adrenal fatigue.

Chronic stress can affect the hypothalamic-pituitary-adrenal (HPA) axis, the system that controls how the brain and the adrenal glands regulate cortisol, your main stress hormone. With long-term stress, this communication system can become less balanced, meaning cortisol may not follow its normal daily rhythm [13]. This can feel like low energy in the morning, feeling alert or restless at night, and being more sensitive to stress. The gut microbiome may also interact with this system by sending signals that help shape how the body responds to stress [4].

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Popular term	What’s actually happening	Gut’s role
“Adrenal fatigue”	Often reflects chronic stress and HPA axis dysregulation	Gut imbalances may increase inflammation and stress signaling
HPA axis dysregulation	Altered cortisol rhythm: feeling tired in the morning and ‘wired but tired’ in the evening	Gut microbes help regulate the gut-brain axis [4]
Adrenal insufficiency	Addison’s disease, a rare medical condition requiring specialist care	Not caused by gut microbiome imbalances [14]

Gut health and chronic fatigue

Studies on ME/CFS have identified gut microbiome patterns that may be linked to persistent fatigue.

Researchers have observed:

• Lower levels of short-chain fatty acid (SCFA) producing bacteria, such as Faecalibacterium prausnitzii, Roseburia, and Eubacterium rectale [15], [16]
• Reduced microbial diversity, but only in some chronic fatigue cohorts [16], [17]
• Increased gut permeability, which means the gut lining is more open, allowing bacteria or bacterial parts to move into the body [7], [17]

However, interpreting these findings is not straightforward. One major challenge is that many people with ME/CFS also have irritable bowel syndrome (IBS), which itself strongly affects the gut microbiome. In fact, some studies found that having IBS was the strongest driver of microbiome differences, sometimes masking patterns specific to ME/CFS [15], [18].

More recent research has also shown that ME/CFS, post-viral fatigue, and long COVID share some overlapping microbiome features [19].

These findings do not prove that gut bacteria cause chronic fatigue, but they suggest the microbiome may influence symptoms in some people.

Practical steps to restore energy through gut health

If you’re dealing with gut health issues and low energy, we recommend you start with the basics before trying expensive supplements or restrictive diets.

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Phase	Timing	Focus	What to Track
Rule out medical causes	Week 1	Bloodwork: check iron, B12, thyroid, vitamin D, glucose	Lab results and symptoms
Foundations	Weeks 1–2	Sleep, hydration, protein intake, morning light, physical activity	Energy and sleep quality
Microbiome support	Weeks 2–8	Fiber diversity and fermented foods	Digestion and bowel habits
Targeted interventions	After healthcare practitioner evaluation	Personalized probiotics or nutrition changes	Symptom trends over time

Foods that support energy and the gut 

• Fiber-rich plants like beans, oats, berries, nuts, and vegetables
• Fermented foods like yogurt, kefir, kimchi, and sauerkraut
• Adequate protein, especially at breakfast [20]
• Omega-3-rich foods like salmon, chia seeds, and walnuts [21]
• Plenty of water throughout the day [22]

Aiming for 25–30 different plant foods each week helps support microbial diversity.

Lifestyle habits that move the needle

• Keep a regular sleep-wake schedule
• Try to spend 20–30 minutes outdoors in natural sunlight before 10 AM [23]
• Reduce excessive alcohol and late caffeine consumption
• Manage stress with movement, mindfulness, or social connection
• Avoid unnecessary antibiotics when possible

Small daily habits often matter more than quick fixes.

How Tiny Health can help identify energy-sapping gut patterns

An at-home gut microbiome test may help uncover patterns linked to inflammation, low microbial diversity, or imbalances that could be contributing to low energy.

An Adult Gut Health Test looks at beneficial bacteria, inflammatory patterns, and functional pathways connected to digestion, immune balance, and gut-brain communication.

Instead of guessing, personalized microbiome insights may help guide more evidence-based gut health decisions.

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