Fatigue is common, affecting up to 45% of people; however, despite this, it is a symptom that can be easily overlooked by healthcare professionals, leading many to suffer without proper care and resolution. While a variety of factors can cause fatigue, the importance of nutrition should be considered in every case. Malnutrition leads to fatigue by failing to provide individuals with adequate caloric and nutritional intake. For those seeking help managing fatigue through diet, keep reading to learn about the most important foods to avoid and incorporate into your meal plans.

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Understanding Fatigue: A Quick Glance

One of the challenges healthcare providers encounter when assessing fatigue lies in the broad and subjective nature of the term used by patients. Fatigue is a complex phenomenon, and individuals may interpret and describe their experiences differently. For example, men typically describe fatigue by saying they feel tired, whereas women will say they feel depressed or anxious (36).  

Fatigue and tiredness are terms often used interchangeably, but there is a distinct difference between fatigue and tiredness. Tiredness generally refers to a feeling of weariness, drowsiness, or a need for sleep after physical or mental exertion. It is a natural response to activities, lack of sleep, or stress and usually improves with rest. (13) 

Fatigue is a more persistent and profound state defined as "an unpleasant physical, cognitive and emotional symptom described as a tiredness not relieved by common strategies that restore energy." It goes beyond the normal feelings of tiredness and can interfere significantly with a person's ability to function effectively in daily life. Fatigue is often accompanied by feelings of weakness, changes in mood, and a reduced capacity to concentrate or complete tasks. Unlike tiredness, fatigue is not always relieved by rest, and the causes of fatigue extend beyond just a lack of sleep. Various factors, including chronic illnesses, hormonal imbalances, poor nutrition, and psychological stress can cause fatigue. (12, 35) 

How Nutrition Affects Energy Levels

Nutrition plays a fundamental role in determining energy levels within the human body. When we consume food, the body uses digestive processes to break down food into a form that can be absorbed and used for fuel. Digestion begins in the mouth, where enzymes start to break down carbohydrates into sugars. The partially digested food then travels to the stomach and small intestine, where proteins are broken down into amino acids, and fats are broken down into fatty acids and glycerol. These smaller molecules are absorbed into the bloodstream through the small intestine and transported to cells throughout the body. (34) 

Once these nutrients enter the cells, the body's metabolism kicks in. Metabolism encompasses all the chemical reactions that occur within the body to maintain life. One of the primary functions of metabolism is to convert macronutrients – carbohydrates, proteins, and fats – into cellular energy (in the form of ATP). Carbohydrates are the body's preferred energy source; they are quickly converted into glucose, which cells use for immediate energy or store as glycogen in muscles and the liver. Proteins can also be converted into energy when carbohydrates are scarce. Fats, stored in adipose tissue, act as a long-term energy reserve. During periods of low food intake, the body breaks down fat into fatty acids and glycerol to provide energy. (2) 

While required by the body in smaller amounts than macronutrients, micronutrients (vitamins and minerals) act as essential cofactors for the enzymes involved in the biochemical pathways involved in energy production. A deficiency in any micronutrient can impair these processes, leading to decreased energy production and fatigue. (26)

Functional Medicine Labs to Assess Fatigue and Nutrition Status

Functional medicine labs are vital tools in evaluating fatigue primarily because the causes of fatigue are incredibly diverse and complex. Unlike conditions with specific and identifiable symptoms, fatigue can be a symptom of numerous underlying issues. This extensive differential diagnosis necessitates a comprehensive and detailed evaluation to identify the root cause accurately. Functional medicine labs are designed to provide in-depth insights into various physiological markers and processes within the body related to hormone levels, immune function, digestive health, and nutritional status.

Complete Blood Count (CBC)

A CBC is a blood test that measures different components of the blood, including red blood cells (RBCs), white blood cells (WBCs), and platelets. It is a general screening test that can provide valuable information that may aid in assessing potential causes of fatigue and nutritional deficiencies.

RBCs contain hemoglobin, a protein that carries oxygen from the lungs to the rest of the body. Low levels of RBCs or hemoglobin are diagnostic for anemia, which leads to insufficient oxygen delivery to tissues and vital organs and causes fatigue as a predominant symptom. Anemia can be caused by deficiencies in iron, vitamin B12, and folate, and abnormal RBC indices on a CBC can signal the need for further investigation into these micronutrients.

Comprehensive Metabolic Panel (CMP) 

A CMP is a blood test that provides information about the body's fluid balance, electrolyte levels, and general metabolism. While it is not specifically designed to diagnose nutritional deficiencies, a CMP can still offer valuable insights into potential causes of fatigue and certain nutritional imbalances by including measurements of electrolytes, blood sugar, protein levels, and liver/kidney function. 

Hormones

Hormones are chemical messengers that regulate various physiological processes, including metabolism, growth, mood, and reproductive functions. Nutrients from the food we eat play a vital role in the production, regulation, and function of hormones. Several types of hormonal imbalances can occur when the body lacks essential nutrients due to poor nutrition. (8) 

Insulin is a hormone that regulates blood sugar levels. Poor nutrition, particularly excessive consumption of sugary foods and refined carbohydrates, can lead to insulin resistance, where cells in the body no longer respond appropriately to insulin. This condition is often associated with poor dietary choices and can contribute to the development of type 2 diabetes.

The production of thyroid hormones depends on many key nutrients, including iodine, iron, tyrosine, zinc, selenium, magnesium, and vitamins E, B2, B3, B6, C, and D. Thyroid hormones are essential for regulating metabolism. Poor nutrition can impair thyroid function, leading to conditions like hypothyroidism (underactive thyroid) or hyperthyroidism (overactive thyroid), which can both present with fatigue as a symptom.

Sex hormone imbalances can lead to various symptoms related to mental, emotional, and physical health. In men, high estrogen and low testosterone levels are linked to higher rates of fatigue and depression. In women, studies have found that higher estrogen and lower progesterone levels are associated with more significant fatigue. Sex hormones can be measured via blood, saliva, and urine. For example, the Female Hormone and Male Hormone panels use a blood sample to measure the primary reproductive hormones to identify imbalances that could manifest as fatigue. 

Adrenal fatigue is a syndrome that describes a constellation of symptoms, including chronic fatigue, commonly associated with high levels of stress and HPA axis dysfunction. During chronic stress, the body's demand for micronutrients, including B vitamins, magnesium, vitamin C, and zinc, increases and can quickly lead to nutritional deficiencies. Advanced adrenal testing uses salivary samples to measure cortisol levels throughout the day. Abnormal patterns can indicate HPA axis dysfunction. 

Micronutrients Test to Assess Essential Vitamins & Minerals for Energy

Due to their roles in ATP synthesis, DNA function, neuronal signaling, and other vital physiological processes, deficiencies in B vitamins, iron, and magnesium correlate to mental and physical fatigue. 

B vitamins, encompassing vitamin B1 (thiamine), B2 (riboflavin), B3 (niacin), B5 (pantothenic acid), B6 (pyridoxine), B7 (biotin), B9 (folate), and B12 (cobalamin), are cofactors in various enzymatic reactions involved in the conversion of carbohydrates, proteins, and fats into ATP. These vitamins are found naturally in various dietary sources, including whole grains, nuts, seeds, vegetables, and animal products. Each vitamin plays a unique role in energy metabolism, and deficiency in any one can lead to reduced energy levels. (41) 

Iron deficiency is one of the most common nutritional deficiencies in the world, affecting an estimated 1.6 billion people worldwide. Additionally, iron deficiency is the most common cause of anemia. Iron deficiency with and without anemia commonly presents with fatigue and weakness. Studies show that correcting iron deficiency and maintaining optimal iron levels improves fatigue. (8, 11) 

Magnesium plays a vital role in producing and utilizing ATP. ATP molecules bind to magnesium ions to form biologically functional complexes. In the mitochondria, these complexes facilitate efficient energy delivery within the cell. Additionally, magnesium acts as a cofactor and regulates enzymes involved in energy biosynthesis pathways, including glycolysis and the citric acid cycle. (41) 

A micronutrient panel can identify deficiencies in these nutrients and other essential ones, such as vitamin D, vitamin C, zinc, and CoQ10, that can lead to fatigue and weakness when depleted.

Top Foods that Boost Energy

Accumulating evidence supports the connection between a pro-inflammatory status and the occurrence of fatigue related to chronic disease. Making dietary changes that follow anti-inflammatory diet principles can improve fatigue and related symptoms. For individuals trying to optimize daily energy levels, try incorporating more of these energy-boosting foods into your meal plans: 

Whole Grains

Whole grains are rich in complex carbohydrates, fiber, vitamins, and minerals, making them a valuable source of sustained energy. Unlike refined grains, whole grains contain all parts of the grain – the bran, germ, and endosperm – which preserve essential nutrients and dietary fiber. The body digests whole grains more slowly due to their complex structure, leading to a gradual release of glucose into the bloodstream. This slow and steady release of energy helps maintain stable blood sugar levels, preventing sudden spikes and crashes that can cause fluctuations in energy. Whole grains also provide essential B vitamins, iron, and magnesium, which play roles in cellular metabolism and oxygen transport. Whole grains are an excellent choice for enhancing stamina and sustaining energy levels by providing a consistent source of nutrients and energy. (24, 37)

Lean Proteins

Proteins are broken down into amino acids, which are then used to produce energy when carbohydrates and fats are unavailable. Certain amino acids can be converted into glucose through a process called gluconeogenesis, providing a steady supply of energy. Additionally, the body uses amino acids as building blocks to synthesize neurotransmitters and hormones that regulate energy metabolism, mood, and cognition. (3) 

Protein is essential for the growth, repair, and maintenance of muscles. Muscles are a reservoir for energy; individuals with well-developed muscles tend to have higher energy levels and endurance. Adequate protein intake supports muscle health, improving physical performance and sustained energy during activities (10). 

Protein-rich foods have a minimal impact on blood sugar levels compared to carbohydrates. Including protein in meals helps stabilize blood glucose levels, preventing rapid spikes and crashes in energy commonly associated with high-carbohydrate meals. 

Nuts and Seeds

Nuts and seeds are not only quick-energy sources but also nutrient-dense powerhouses. Their optimal blend of healthy fats, proteins, carbohydrates, vitamins, minerals, and fiber makes them ideal for supporting sustained energy levels, promoting overall health, and combating fatigue. (27) 

Fresh Fruits

Fresh fruits contain natural sugars like fructose and glucose, providing quick energy. Unlike refined sugars, the natural sugars in fruits are accompanied by fiber, vitamins, and minerals, ensuring a balanced energy release without the rapid blood sugar spikes and crashes associated with processed sweets. Fruits are also rich in antioxidants, which protect cells from oxidative stress and inflammation. Some of the best fruits for energy levels include bananas, dark berries, and avocados. (27)

Green Leafy Vegetables

Leafy greens, such as kale, arugula, and spinach, are healthy carbohydrate sources that contain various nutrients and bioactive compounds, including niacin, flavonoids, carotenoids, and sulforaphane. These compounds are antioxidant and anti-inflammatory. Additionally, green leafy vegetables are iron-rich, making them an excellent plant-based iron dietary source. Anti-inflammatory diets proven to reduce fatigue emphasize the intake of green leafy vegetables because of their wide array of associated health effects. (42) 

Hydration: The Often-Overlooked Factor

Adequate hydration is essential for efficient digestion, nutrient absorption, and transporting vitamins and minerals throughout the body. Water also supports the elimination of waste products and toxins, aiding the kidneys in filtering out impurities from the bloodstream. (5, 20)

Dehydration, on the other hand, can have significant adverse effects on energy levels and contribute to fatigue. When the body lacks sufficient water, blood volume decreases, reducing oxygen delivery to cells and tissues. This decreased oxygen supply hampers the body's ability to produce energy and impairs cognitive function, leaving individuals tired and sluggish. (5)

Water intake recommendations vary between individuals, depending on factors like activity levels, weight, age, and climate. General recommendations suggest drinking half of your body weight (in pounds) in ounces daily. People exercising should drink 16-20 ounces of water beforehand, consume water every 10-15 minutes during, and drink at least 16-24 ounces afterward to replace the water they've lost. (17)

Limiting Energy-Zappers

Limiting foods that cause fatigue is equally important as incorporating nutrient-dense foods into the diet when supporting optimal energy levels.

Sugary drinks, laden with added sugars, can lead to rapid spikes in blood sugar levels, followed by sharp crashes, causing feelings of fatigue and low energy. 

Caffeine, while providing a temporary energy boost, can disrupt sleep patterns and lead to restlessness when consumed in excess. Caffeine is a stimulant that blocks the action of adenosine, a neurotransmitter that promotes sleep and relaxation. As the stimulating effects wear off, individuals can experience an energy crash, leaving them feeling more tired than before consuming caffeine. Caffeine is also a diuretic, and excess consumption can lead to dehydration. Dietary guidelines recommend limiting caffeine intake to no more than 400 mg daily. (19)

Alcohol, a depressant and sedative, affects the central nervous system, impairing cognitive function and physical coordination, often leading to fatigue and sluggishness. Alcohol use is also strongly associated with sleep disruptions, accounting for up to 10% of chronic insomnia, which can further exacerbate low energy. (1)

The Role of Meal Timing and Portion Sizes

Regular, balanced meals sustain energy levels. When meals are spaced throughout the day and contain a proper balance of carbohydrates, proteins, and healthy fats, the body receives a steady supply of nutrients and energy. This consistent intake helps regulate blood sugar levels, preventing rapid spikes and crashes. By avoiding prolonged periods without food, individuals can maintain stable energy levels, support cognitive function, and ensure optimal physical performance. 

Conversely, overeating can lead to feelings of fatigue. Consuming excessive calories, especially from high-sugar and high-fat foods, can cause rapid increases in blood sugar levels followed by sharp drops. These fluctuations can result in energy crashes, leaving individuals lethargic. Moreover, the body redirects blood flow from other organs to the digestive tract and expends a significant amount of energy digesting large meals, causing a temporary dip in energy levels afterward. (33) 

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Summary

With so much conflicting nutrition information, knowing how to eat can feel overwhelming. While there is no "right" diet for everyone, it cannot be disputed that our dietary choices influence our mood and energy levels. Choosing foods that reduce inflammation, balance blood sugar, and provide the body with adequate macro- and micronutrients to support healthy metabolism can sustain energy levels throughout the day and resolve chronic fatigue.