By Kim Plaza


If you’re suffering from a bout of 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. 


The term ‘fatigue’ is often used to describe extreme tiredness or exhaustion, resulting from mental or physical exertion or illness. Fatigue can be classified as secondary, physiological, or chronic. Secondary fatigue is caused by an underlying medical condition or medication and generally lasts less than six months.1 

Physiological fatigue is caused by an imbalance in the routines of exercise, sleep, diet, or other activity. It is not caused by an underlying medical condition and is relieved with rest.1 

Chronic Fatigue Syndrome (CFS) is persistent or recurrent debilitating fatigue, that is not the result of ongoing exertion, or alleviated by rest, or explained by other conditions and results in a substantial reduction in activity.2 Whilst secondary fatigue and CFS should be assessed by a medical practitioner, there are some physiological causes of fatigue that may be overcome by changes in our daily habits. Here are seven that you may not have known about.



Although exercise may be an obvious culprit concerning fatigue, it might not be obvious that changing up your routine could have an impact upon 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 need to 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.3

Chronic overtraining is described as the late stage of intense and prolonged training during which the exercise performance declines instead of becoming progressively better.3 Therefore it’s often highlighted that rest is as important as training. So, if you feel that your workout is getting much tougher 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.3 Supporting the stress response, that may have become dysregulated as a result of overtraining, may allow us to overcome the physiological effects of exercise-induced fatigue. Rest is of course paramount, as it allows the equilibrium of stress-related hormones to rebalance. Consider sufficient protein consumption as well as 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.5,6



Fatigue can be tricky to define, as it is a subjective experience. However, whilst everyone feels tired, sleepy or over-worked from time-to-time, it’s important to distinguish instances of temporary fatigue, which usually have an identifiable cause and a likely remedy, from on-going 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, which inevitably leads 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 important biological mechanism and getting restorative sleep requires a balance of hormones that are governed by a many factors; including light exposure, food intake and timing, as well as hydration levels.8–10 Be prepared for it to take some time before getting restful sleep and improving fatigue, especially 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. Make a note of 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 lead to hormones being released to deal with the additional load. 

Setting a sleep promoting environment is also useful for 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 useful for many people, so consider a varied intake of fruits and vegetables, with sufficient content of magnesium and vitamin B6 (such as nuts, seeds, wholegrains, 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 the symptoms of fatigue, possibly through the mechanisms of 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’.13–15 

When protein and energy intakes fail to meet a person’s need, body stores are broken down to provide energy, leading to the depletion of body fat and muscle,16,17 with consequent symptoms such as fatigue.13,15 There also appears to be a bi-directional association between undernutrition and fatigue. Whilst undernourished people are more prone to experience fatigue symptoms, fatigued people may be at risk of undernutrition due to lack of 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. Whilst 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 of an 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 therefore compliment stress hormone regulation – another possible factor in extreme fatigue.




Supporting a healthy microbial balance in the gut is important for energy levels for numerous reasons. Beneficial species produce a variety of compounds, including B vitamins which are important 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 not only provide a fuel source for the cells of the gut lining, but also play an important role in maintaining overall energy levels. In fact, 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 important role that the gut microbiota plays in mental and cognitive health via the microbiota-gut-brain axis. With fatigue being a common symptom in many psychiatric and neurodegenerative conditions. Supporting gut health may also have a positive effect on 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, as well as 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 contributes to the reduction of tiredness and fatigue.20



Now we understand the fundamental role many vitamins and minerals play in the biochemical processes of energy generation, it’s clear micronutrients are key in optimizing energy processing roles such as glycolysis, the 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 choose to supplement with vitamins and minerals, make sure you opt for a good quality product. There is also evidence of the essential role that the B vitamin family plays 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 that fatigue is associated with poor nutrient status.



In an acute phase, our bodies are well adapted 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. 

Recovery from acute stress happens fairly rapidly, and hormone levels should normalize quickly after an event. However, our bodies are not so well adapted to dealing with chronic stress, which can leave us with a host of 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 (which are often symptoms associated with fatigue). Some people also notice a worsening of conditions such as irritable bowel syndrome or migraines. One study noted that stress and fatigue symptoms overlap,24 therefore reducing levels of stress would likely reduce symptoms of fatigue.

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 in this regard, as can meditation and practicing mindfulness. Everyone feels better able to cope when they’ve had a good night’s sleep, so as 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 on a minute-by-minute basis. 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 a variety of 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 is not to suggest that a person has a set chance of experiencing fatigue or CFS, however it may be useful to take note of your environment as well as people you socialize with. This could increase awareness of how these factors impact you daily. One study found differences between men and women on their levels of fatigue, based on whether they had positive or negative same-day interpersonal events.27 

The polyvagal theory suggests that self-regulation may be dependent upon 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 are able to recognize that our environment does not pose a threat or stress, the better we are able to 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 about 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 seems bewildering at first, there are many podcasts that guide you through this exercise. Calming the body via the vagus nerve may also be a valuable strategy for combatting fatigue.


Hectic schedules in our busy lives can throw energy levels out of whack, here’s HOW TO BEAT BURNOUT IN 7 DAYS


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