Energy & Fatigue

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    Last Updated: August 16, 2022

    Energy is the ability to do work. In humans, energy affects the ability to sustain physical and cognitive activity, and may also refer to the subjective experience of being able to do so. Fatigue is the opposite: a lack of energy, often as a result of exertion or disease.

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    What does energy and fatigue encompass?

    Fatigue is generally defined as extreme tiredness due to exertion or illness, whereas energy refers to the actual or perceived ability to power physical and mental activity. Fatigue in exercise science is slightly different: fatigue is characterized as diminished output in response to sustained effort.[1] The broad topic of fatigue and energy is related to nutrient status, metabolism and energetics (i.e. mitochondria function), exercise, physiology, psychology, neurobiology, oxidative stress, inflammation, sleep, and many body systems. Fatigue can be as mild as feeling tired regularly, or as extreme as the disabling fatigue indicative of a severe medical condition (i.e. chronic fatigue syndrome (CFS), also known as ME/CFS).[2]

    How could diet affect energy and fatigue?

    Food choice is foundational for sustaining energy, as calories are metabolized into ATP, the primary source of energy that fuels cell needs. Healthy, nutrient dense dietary patterns support the energetic demands of life, prevent conditions that increase risk for fatigue, and have been used in studies to reduce fatigue and increase energy.[3][4] Some foods contain nutrients at doses shown to support energy and resist fatigue either in general (e.g., iron in red meat) or during exercise (e.g., nitrates in spinach).[5]

    Which supplements are of most interest for energy and fatigue?

    Getting enough essential vitamins and minerals (e.g., iron for blood cell function, B-complex vitamins for metabolism support) is foundational in any approach designed to address fatigue, which means that supplementation can be beneficial if the diet does not provide enough of these nutrients.

    The most common supplements used for increasing mental and physical energy are stimulants (e.g., caffeine, guarana). Supplements that improve cognitive function, like nootropics, are also related to increasing energy.

    Supplements that increase endurance, support fatigue resistance, promote stress tolerance, or have another effect on enhancing exercise (such as ergogenics) are relevant to energy and fatigue.

    Examine Database: Energy & Fatigue

    Frequently asked questions

    What does energy and fatigue encompass?

    Fatigue is generally defined as extreme tiredness due to exertion or illness, whereas energy refers to the actual or perceived ability to power physical and mental activity. Fatigue in exercise science is slightly different: fatigue is characterized as diminished output in response to sustained effort.[1] The broad topic of fatigue and energy is related to nutrient status, metabolism and energetics (i.e. mitochondria function), exercise, physiology, psychology, neurobiology, oxidative stress, inflammation, sleep, and many body systems. Fatigue can be as mild as feeling tired regularly, or as extreme as the disabling fatigue indicative of a severe medical condition (i.e. chronic fatigue syndrome (CFS), also known as ME/CFS).[2]

    Who is most at risk for fatigue?

    People with chronic conditions, taking certain medicines, receiving medical treatments like chemotherapy and radiation, or recovering from major surgery, injury, or illness are at high risk for fatigue. Risk for everyday fatigue increases when sleep onset occurs later than usual, with circadian disruption, and after drinking too much alcohol. Other populations at risk for fatigue include people losing weight, older adults, shift workers, and women, especially women who are pregnant. [6]

    What is Adrenal Fatigue?
    Quick answer:

    Adrenal fatigue is medically referred to as adrenal insufficiency — a dysregulation of the HPA axis that results in the reduction of hormones that regulate mood and energy.

    What is Adrenal Fatigue

    'Adrenal Fatigue' is more of a marketing term than anything, to refer to a variety of symptoms associated with underactive set of adrenal glands. This condition, medically referred to as 'Adrenal Insufficiency', is usually when the adrenal glands become hyporesponsive (underresponsive) to signals sent from the brain to secrete hormones.[8] This, however, is not solely to place blame on the adrenal glands; abnormal effects can occur at a variety of points.[9]

    Mechanistically, the Hypothalamus (a brain structure) perceives stress and secretes Corticotropin Secreting Hormone (CRH) which acts on the pituitary. The pituitary then releases _Adreno_corticotropin Hormone (ACTH) which goes to act upon the adrenal glands, which rest on top of the kidneys. The interaction of these three organs is known as the Hypothalamus-Pituitary-Adrenal axis, or the HPA Axis.

    Primary Adrenal insufficiency is when the adrenal glands themselves respond less to secreted ACTH or are otherwise damaged, and despite the hypothalamus and pituitary working fine the adrenal glands do not secrete the hormones required of them; cortisol and dehydroepiandrosterone. This can be diagnosed with an ACTH-stimulation test by an endocrinologist, and the main pathology is less secretion and synthesis of cortisol.

    Secondary Adrenal insufficiency is either a hypothalamus that secretes less CRH, or a pituitary that secretes less ACTH, in response to stress. The adrenal glands themselves function normally in this scenario, but do not receive the signal to create more hormones. ACTH can be measured in the blood by a medical doctor, but CRH is difficult to measure practically due to it being localized in the brain.

    Sometimes, deficiency is CRH is referred to as tertiary adrenal insufficiency.[9]

    Thus, 'adrenal insufficiency' is a dysregulation in the HPA axis that ultimately results in less secretion of hormones that can regulate mood and energy. It really isn't one mechanism or event, but a term used to refer to the ultimate state of less hormones and dysregulation in this system

    How could diet affect energy and fatigue?

    Food choice is foundational for sustaining energy, as calories are metabolized into ATP, the primary source of energy that fuels cell needs. Healthy, nutrient dense dietary patterns support the energetic demands of life, prevent conditions that increase risk for fatigue, and have been used in studies to reduce fatigue and increase energy.[3][4] Some foods contain nutrients at doses shown to support energy and resist fatigue either in general (e.g., iron in red meat) or during exercise (e.g., nitrates in spinach).[5]

    Which supplements are of most interest for energy and fatigue?

    Getting enough essential vitamins and minerals (e.g., iron for blood cell function, B-complex vitamins for metabolism support) is foundational in any approach designed to address fatigue, which means that supplementation can be beneficial if the diet does not provide enough of these nutrients.

    The most common supplements used for increasing mental and physical energy are stimulants (e.g., caffeine, guarana). Supplements that improve cognitive function, like nootropics, are also related to increasing energy.

    Supplements that increase endurance, support fatigue resistance, promote stress tolerance, or have another effect on enhancing exercise (such as ergogenics) are relevant to energy and fatigue.

    What are energy drinks good for?

    The International Society of Sports Nutrition’s position statement on energy drinks[7] suggests that the main ergogenic (athletic enhancing) ingredients are caffeine and sugar. Caffeine provides mental focus, alertness, and improves performance while sugar provides quick energy. A review confirms this position and presents some evidence to support improvements in cognitive performance from energy drinks, but suggests there are adverse effects (metabolic, dental, sleep, stress, and more) that may outweigh the positives.

    References

    1. ^Wan JJ, Qin Z, Wang PY, Sun Y, Liu XMuscle fatigue: general understanding and treatment.Exp Mol Med.(2017-10-06)
    2. ^Committee on the Diagnostic Criteria for Myalgic Encephalomyelitis/Chronic Fatigue Syndrome, Board on the Health of Select Populations, Institute of MedicineBeyond Myalgic Encephalomyelitis/Chronic Fatigue Syndrome: Redefining an Illness
    3. ^Centers for Disease Control and PreventionPoor Nutrition(2022 May)
    4. ^Zick SM, Colacino J, Cornellier M, Khabir T, Surnow K, Djuric ZFatigue reduction diet in breast cancer survivors: a pilot randomized clinical trial.Breast Cancer Res Treat.(2017-01)
    5. ^Jonvik KL, Nyakayiru J, Pinckaers PJ, Senden JM, van Loon LJ, Verdijk LBNitrate-Rich Vegetables Increase Plasma Nitrate and Nitrite Concentrations and Lower Blood Pressure in Healthy Adults.J Nutr.(2016-05)
    6. ^The content of this page was partially adapted from MedlinePlus of the National Library of Medicine
    7. ^Campbell B, Wilborn C, La Bounty P, Taylor L, Nelson MT, Greenwood M, Ziegenfuss TN, Lopez HL, Hoffman JR, Stout JR, Schmitz S, Collins R, Kalman DS, Antonio J, Kreider RBInternational Society of Sports Nutrition position stand: energy drinksJ Int Soc Sports Nutr.(2013 Jan 3)
    8. ^Li-Ng M, Kennedy LAdrenal InsufficiencyJ Surg Oncol.(2012 Jul 17)
    9. ^Salvatori RAdrenal insufficiencyJAMA.(2005 Nov 16)