From a functional medicine perspective, the causes of chronic or persistent fatigue can vary widely from food intolerances, traumatic emotional stress, viral infections, nutritional deficiencies, anemias and environmental toxin exposure. Fatigue is one of the most common symptoms that patients report to health care practitioners.

The average American gets almost 70 percent of calories from flour, sugar, industrialized plant oils, alcohol and dairy products. One-third of Americans get fewer than six hours of sleep per night, despite a mountain of evidence indicating that we need seven to eight hours to function properly. According to the American Institute of Stress, 77 percent of people regularly experience physical symptoms with fatigue at the top of the list due to chronic stress.

Fatigue is a term used to describe an overall feeling of tiredness or lack of energy. Being sleepy may be a symptom of fatigue, but it’s not the same thing. While many people think that having low energy is a by-product of not getting enough sleep, it can be more serious and actually the symptom of Chronic Fatigue Syndrome.

Fatigue symptoms include: Feeling weak, constantly tired, lack of energy, weight loss or weight gain, chest pain and shortness of breath, vomiting and diarrhea, fevers and chills, muscle weakness or pain, and anxiety and depression.

Poor diet, lack of sleep and chronic stress are the most common causes of fatigue. If you do eat right, get sleep and manage stress and still feel tired all the time, you are often diagnosed with depression or anxiety and prescribed antidepressants. Antidepressants are rarely successful because they fail to address the real underlying causes of fatigue.

There are other less obvious causes of fatigue to be aware of:

Chronic Infections: Several studies have found that patients complaining of chronic fatigue have lab markers consistent with active pathogen activity and infection. These infections may be either viral or bacterial. Diagnosing these chronic infections is challenging and fraught with controversy. This is in large part because these organisms are experts at evading our immune system and thus difficult to test for.

Biotoxin Illness: A biotoxin is a poisonous substance produced by living organisms. These biotoxins are found in water-damaged buildings, marine or freshwater environments and in microorganisms that infect humans. The persistence of these biotoxins in the body then sets off a chain reaction of biochemical events, leading to a continuous upregulation of multiple inflammatory pathways, reduced blood flow, a dysregulated immune system, hormone imbalance, intestinal permeability and disrupted neurological function.

Impaired Methylation: Methylation is a complex biochemical process. Methylation is required to produce CoQ10 and carnitine, which are essential for producing cellular energy. It also regulates gene expression, strongly influences detoxification, regulates folate metabolism and promotes normal immune function. Studies indicate that genetic mutations which affect the methylation pathway are associated with chronic fatigue.

Mitochondrial Dysfunction: Mitochondria are known as the “battery” or energy powerhouse of the cell. They are also involved in the production of reactive oxygen species, regulation of amino acids, metabolites, enzyme cofactors, neurotransmitter synthesis, insulin secretion, and pyrimidine and lipid production. Mitochondrial dysfunction has been linked not only to fatigue but to a wide range of health conditions like cancer, diabetes, fibromyalgia and serious mental disorders like schizophrenia and bipolar disease. It can range from relatively mild to life-threatening.

Gut Dysfunction: There are numerous pathologies related to gut health that are associated with fatigue, including small intestinal bacterial overgrowth, chronic infections, dysbiosis and fungal overgrowth, intestinal permeability and food intolerances.

There are many conditions that can cause persistent, unexplained fatigue that interferes with daily activities for more than six months. These can include hypothyroidism, Lyme disease, asthma, diabetes, obstructive sleep apnoea, rheumatoid arthritis, fibromyalgia and heart disease.

Not eating enough or eating foods that are not nutritious can cause fatigue. Here are some things to that will help:

Try an anti-inflammatory diet, adding fish and olive oil; limit inflammatory foods like sugar, fried foods and processed meat; limit caffeine intake; try smaller meals more frequently or add small snacks between each meal; decrease your sugar consumption; fill up on nonstarchy vegetables; limit processed foods; and include healthy fats.

You can also be aware of some lifestyle factors that play a factor: Physical exertion; lack of physical activity; lack of sleep; being overweight or obese; periods of emotional stress; boredom; grief; using alcohol on a regular basis; and using illicit drugs, such as cocaine.

Certain medications may cause fatigue as a side effect. These include blood pressure medications, diuretics, antidepressants, antihistamines, statins, proton pump inhibitors, benzodiazepines, antibiotics and antipsychotics.

When we perceive that we are in danger, we have a fight or flight response that prepares us to either run away or stay and fight. In order to do this, our body releases hormones that cause our heart to beat faster, increase blood sugar to fuel your muscles and increase the rate of breathing. Ongoing stress can turn into adrenal fatigue, which causes a host of symptoms.

Several hormones can contribute to fatigue. Your thyroid powers every cell in your body through the hormones it produces. If you have thyroid problems, then you will most likely have fatigue. Chronic stress can also overwhelm the adrenal gland, crucial in producing and distributing hormones.

There are some other areas to be aware of that will help. They include REM sleep (important for normal brain function and development); not drinking enough water (aim to drink 8 glasses of water a day); mold exposure (have your home tested to see if you have been exposed); and mercury poisoning (has been traced to amalgam fillings for your teeth). 

The conventional medical system is not set up to deal with chronic fatigue. It is based more on disease management or symptom suppression with drugs than it is on identifying the underlying cause or disease. This is where a functional medicine approach can be helpful.