Seven Causes of Extreme Fatigue

Seven Causes of Extreme Fatigue

Author: Kim Plaza

If you’re suffering from extreme fatigue, consult Muscle and Health’s seven top culprits as your first point of call to help alleviate your symptoms and energize your life. 

Fatigue often describes extreme tiredness or exhaustion resulting from mental or physical exertion or illness. Fatigue can be classified as secondary, physiological, or chronic. An underlying medical condition or medication causes secondary fatigue and lasts less than six months.

An imbalance in the routines of exercise, sleep, diet, or other activity causes physiological fatigue. It is not caused by an underlying medical condition and is relieved with rest. 

Chronic Fatigue Syndrome (CFS) is persistent or recurrent debilitating fatigue that is not the result of ongoing exertion, alleviated by rest, or explained by other conditions and results in a substantial reduction in activity. While a medical practitioner should assess secondary fatigue and CFS, some physiological causes of fatigue changes in our daily habits may be overcome. Here are seven that you may not have known about.



Although exercise may be an obvious culprit concerning fatigue, it might not be evident that changing your routine could impact fatigue levels and adaptability. Exercise intensity, endurance, timing and type are all variables that cause different effects within the body systems.3 Physical exercise brings about a whole range of changes, affecting the biochemical equilibrium of the exercising muscle, including protons, lactate and free magnesium accumulation. Nutrients must be supplied to this working muscle to restore chemical balance and adapt to the workout, meaning that energy stocks are depleted from elsewhere in the body. Inflammatory compounds are also released, which affects other organs, including the brain. Collectively, these mechanisms result in fatigue and can be seen as a debt that the body must restore in the form of rest.

Chronic overtraining is described as the late stage of intense and prolonged training during which the exercise performance declines instead of becoming progressively better. Therefore it’s often highlighted that rest is as important as training. So, if you feel your workout is getting much more challenging than it used to be without changing anything, consider whether you’re overtraining. Many hypotheses about overtraining mention the involvement of inflammation caused by a type of microtrauma. Supporting the stress response that may have become dysregulated due to overtraining may allow us to overcome the physiological effects of exercise-induced fatigue. Rest is paramount, as stress-related hormones’ equilibrium can rebalance. Consider sufficient protein consumption and foods with high antioxidant content, such as berries and grapes.4 Look after your gut too. Glutamine, as well as fermented foods, both have the potential ability to heal the gut lining and support the tight junctions that are vital in modulating inflammation.



Fatigue can be tricky to define, as it is a subjective experience. However, while everyone feels tired, sleepy or overworked occasionally, it’s essential to distinguish temporary fatigue, which usually has an identifiable cause and a likely remedy, from ongoing symptoms of unrelenting exhaustion, which are not relieved by rest.  For example, when we feel sleepy, it can stop us from doing our daily activities, inevitably leading us to fall asleep. This type of sleepiness is often remedied by having a nap or a good night’s sleep.1 Fatigue, on the other hand, is intensified by activity, at least in the short-term,7 with people often reporting a lack of energy, mental exhaustion, poor muscle endurance, delayed recovery after physical exertion, and nonrestorative sleep.1 Fatigue is, therefore, a more constant state of weariness, usually developing over time that can significantly reduce motivation and concentration as well as impact individual’s emotional and psychological well-being.

Sleep is a vitally crucial biological mechanism, and getting restorative sleep requires a balance of hormones that are governed by many factors, including light exposure, food intake and timing, as well as hydration levels. Be prepared for it to take some time before getting restful sleep and improving fatigue, significantly if sleep patterns have been dysregulated for some time. 

Keep a regular day and night-time routine. Getting up and going to bed at similar times each day will help to balance sleep-related hormones. Note your consumption of stimulants and depressants, such as coffee, alcohol, chocolate, energy drinks, and tea. Stimulating food and drink provide a short-term spike in blood glucose levels, which releases hormones to deal with the additional load. 

Setting a sleep-promoting environment is also helpful in getting the body ready for sleep. Turn off the television or other distractions an hour before bedtime, and consider infusions of essential oils and dim lighting to promote relaxation. Diets that support sleep are also often beneficial for many people, so consider a varied intake of fruits and vegetables with good magnesium and vitamin B6 (such as nuts, seeds, whole grains, lean meat, legumes and chickpeas). Alternatively, some choose to supplement. A 2019 study found that those with a higher sleep quality were consuming higher levels of vitamin B6 and magnesium.11



Changes in food intake and body composition seem to influence fatigue symptoms, possibly through inflammation and/or dysregulation of energy cell metabolism (known as mitochondrial dysfunction).12 Undernutrition may result in weight loss and nutritional deficiencies leading to fatigue by means of ‘lack of energy’.

When protein and energy intakes fail to meet a person’s needs, body stores are broken down to provide energy, leading to the depletion of body fat and muscle, with consequent symptoms such as fatigue. There also appears to be a bi-directional association between undernutrition and fatigue. While undernourished people are more prone to experience fatigue symptoms, fatigued people may be at risk of undernutrition due to insufficient energy to prepare substantial meals.14

Many people experiencing extreme fatigue are not eating enough calories. This is important considering the metabolic requirements for normal bodily function. While caloric requirements will vary from person to person (depending upon body composition, basal metabolic rate, genetics and activity levels), the current government recommendations suggest that women need around 2000 calories daily and men need around 2500. Try a variety of protein-rich meals, and try small meals and snacks frequently throughout the day if you don’t have much appetite. This could be as simple as boiled eggs, pumpkin seeds or dry-roasted edamame beans. Switching to higher protein foods may also support good blood sugar balance and complement stress hormone regulation – another possible factor in extreme fatigue.



For numerous reasons, supporting a healthy microbial balance in the gut is essential for energy levels. Beneficial species produce a variety of compounds, including B vitamins which are essential for red blood cell formation (transporting oxygen around the body) and act as co-factors for energy production. Our gut bacteria also produce Short-Chain Fatty Acids (SCFAs) via intestinal fermentation of dietary fiber and resistant starch. SCFAs provide a fuel source for the gut lining cells and play an essential role in maintaining overall energy levels. It has been estimated that SCFAs contribute to around 60–70% of the energy requirements of gut lining cells and 5–15% of the total caloric requirements of humans.18 Beneficial species also support the health of the gut barrier to reduce systemic inflammation, which is commonly associated with symptoms of fatigue. 

Finally, research is uncovering the vital role of gut microbiota in mental and cognitive health via the microbiota-gut-brain axis. Fatigue is a common symptom in many psychiatric and neurodegenerative conditions. Supporting gut health may also positively affect energy levels via this route. So, try to consume a wide variety of plant-based foods containing plenty of prebiotic dietary fiber, resistant starches and polyphenols, to support microbial diversity in the gut, along with traditionally fermented foods such as live yogurt, kefir, sauerkraut and kimchi. 

Supplementing with live bacteria alongside consuming fermented food is evidenced to reduce tiredness, support gut barrier function and produce SCFAs. Bio-Kult Boosted contains 14 different strains of live bacteria that were found to reduce tiredness and stress hormones.19 It also contains vitamin B12, which reduces tiredness and fatigue.20



Now we understand the fundamental role many vitamins and minerals play in the biochemical processes of energy generation. Micronutrients are vital in optimizing energy processing roles such as glycolysis, Kreb’s cycle, electron transport chain and beta-oxidation. Nutrient deficiencies caused by a poor diet (and increased nutrient requirements in some instances) can significantly impact energy production processes, resulting in symptoms of fatigue.

Interestingly, nutritional deficiencies (vitamin C, B vitamins, sodium, magnesium, zinc, folic acid, L-carnitine, L-tryptophan, essential fatty acids, coenzyme Q10) have been reported in people with CFS,21,22 so ensuring adequate consumption of many different colored fruits and vegetables (as well as good quality protein) is hugely important to obtain these nutrients. 

If you supplement with vitamins and minerals, choose a good quality product. There is also evidence of the essential role of the B vitamin family in maintaining energy metabolism, as well as how a deficiency in any of the B vitamins can lead to energy dysregulation.23 Therefore, a good quality B complex is often the first port of call if you feel fatigue is associated with poor nutrient status.



In an acute phase, our bodies adapt well to cope with stress. We get increased blood pressure, heart rate and cognitive function while, at the same time, our digestive and immune systems are inhibited. 

Acute stress recovery happens rapidly, and hormone levels should normalize quickly after an event. However, our bodies are not well adapted to chronic stress, leaving us with many potential problems. Chronic exposure to stress hormones has been shown to affect the area of the brain involved in memory processing and emotional regulation. Therefore, it’s not surprising that common symptoms of stress include feeling anxious, low mood, difficulties sleeping, low energy, poor memory, lack of appetite, comfort eating, and cravings for stimulants or sugary foods (often symptoms associated with fatigue). Some people also notice worsening conditions such as irritable bowel syndrome or migraines. One study noted that stress and fatigue symptoms overlap; therefore, reducing stress levels would likely reduce fatigue symptoms.

We will never be able to completely eradicate stress from our lives, so working to develop resilience to stress is the next best option. Cognitive behavioral therapy (CBT) can be very beneficial, as can meditation and practicing mindfulness. Everyone feels better able to cope when they’ve had a good night’s sleep, so prioritize getting to bed at a reasonable hour and allowing time to wind down beforehand.



Taking note of our surroundings is vitally important as we interact with them minute-by-minutely. The polyvagal theory discusses the impact our autonomic nervous system (which governs heart rate, blood pressure, metabolism, respiration etc.) has on prosocial behaviors. 

This theory suggests that various influences (such as childhood experiences and social behaviors), shape our responses to new and existing environments resulting in positive or negative outcomes.25 For example, if an individual has had adverse childhood experiences, it is posited that their stress responses may be at an increased risk of dysregulation, which could predispose a person to stress-related conditions, including CFS.26 

This does not suggest a person has a set chance of experiencing fatigue or CFS. However, noting your environment and the people you socialize with may be useful. This could increase awareness of how these factors impact you daily. One study found differences between men and women in their fatigue levels based on whether they had positive or negative same-day interpersonal events.27 

The polyvagal theory suggests that self-regulation may depend on the accuracy with which we interpret environmental triggers, with greater accuracy leading to greater adaptability and self-regulation.25 In other words, the more we recognize that our environment does not pose a threat or stress, the better we can adapt and not evoke a stress response. This could imply that with practice, we may become more efficient at calming the stress response and potentially reducing symptoms of fatigue.

Make time for socializing with positive people that you share positive experiences with. Likewise, be aware of people in your life that socially drain you and bring negative feelings. Spending time outdoors in nature is also beneficial. This doesn’t need to involve physical activity but instead could be sitting in a garden or park and taking note of the sounds, smells, and feelings of nature, such as the temperature, breeze and all the other things that are often missed when maintaining a busy lifestyle. If it initially seems bewildering, many podcasts guide you through this exercise. Calming the body via the vagus nerve may also be a valuable strategy for combatting fatigue.


How can exercise contribute to fatigue?

Exercise-induced fatigue can occur due to intense physical exertion that depletes energy stores in the body. It also leads to the release of inflammatory compounds that affect various organs, including the brain. Finding a balance between exercise intensity, endurance, timing, and type is essential to prevent excessive fatigue.

Can lack of sleep cause chronic fatigue?

Yes, chronic lack of sleep can contribute to persistent fatigue. Poor sleep quality or inadequate duration can disrupt the body’s natural restorative processes, leading to persistent tiredness and exhaustion.

Can nutritional deficiencies cause fatigue?

Yes, nutritional deficiencies, particularly in critical micronutrients like vitamins and minerals, can impact energy levels and contribute to fatigue. Ensuring a well-balanced diet that includes a variety of nutrient-rich foods is essential for maintaining optimal energy levels.

How does gut health affect fatigue?

Gut health plays a significant role in overall well-being, including energy levels. A healthy gut microbiome supports the production of essential compounds like B vitamins and short-chain fatty acids, which are involved in energy production and maintaining gut barrier health. Imbalances in gut bacteria can lead to inflammation and potential fatigue symptoms.

Can stress contribute to fatigue?

Chronic stress can profoundly impact mental and physical well-being, often overlapping with symptoms of fatigue such as low mood, low energy levels, difficulties sleeping, and anxiety. Managing stress through techniques like mindfulness, relaxation exercises, or seeking support from mental health professionals can help reduce its impact on overall energy levels.

How long does it take to overcome chronic fatigue?

The time it takes to overcome chronic fatigue can vary depending on individual circumstances and underlying causes. It may require a multi-faceted approach that includes lifestyle changes, medical interventions if necessary (under healthcare professional guidance), proper nutrition, adequate restful sleep, and stress management. Patience, persistence, and working closely with healthcare professionals are essential.

When should I seek medical help for fatigue?

If you experience persistent fatigue that significantly impacts your daily life despite making lifestyle changes, it is essential to consult a healthcare professional. They can help determine whether an underlying medical condition contributes to your fatigue and provide appropriate guidance and treatment options.

Remember that these answers are general, and individual experiences may vary. It is always recommended to consult with healthcare professionals for personalized advice tailored to your specific situation.


Understanding and addressing the various factors contributing to fatigue is essential for improving energy levels and overall well-being. By recognizing the potential culprits, such as exercise-induced fatigue, lack of sleep, undernutrition, poor gut health, micronutrient imbalances, dysregulated stress responses, and unconducive environments, individuals can take proactive steps to alleviate their symptoms.

Seeking guidance from healthcare professionals is crucial in chronic or secondary fatigue caused by underlying medical conditions. However, making changes to daily habits and adopting a holistic approach to self-care can also have a significant impact on reducing fatigue.

By prioritizing restful sleep, maintaining a balanced diet rich in essential nutrients, supporting gut health through dietary choices and supplementation when necessary, managing stress levels effectively, and creating an environment conducive to well-being, individuals can optimize their energy levels and improve their quality of life.

Remember that everyone’s experience with fatigue may vary, and it may take time to find the best strategies that work for each individual. With patience and persistence in implementing positive changes, it is possible to overcome fatigue and reclaim vitality.

Always consult with healthcare professionals for personalized advice tailored to your specific situation.

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