What is a state of low energy, also known as fatigue or lethargy?

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Last updated: February 23, 2025 • View editorial policy

From the Guidelines

A state of low energy, also known as fatigue or lethargy, is a condition where a person feels persistently tired, lethargic, and lacks the motivation or physical capacity to engage in normal daily activities, often resulting from lifestyle factors, nutrient deficiencies, or hormonal imbalances, as noted in the IOC consensus statement on Relative Energy Deficiency in Sport (RED-S) 1, 2, 3. To address a low energy state:

  • Improve sleep habits: Aim for 7-9 hours of quality sleep per night.
  • Exercise regularly: Start with 30 minutes of moderate activity 3-5 times per week.
  • Eat a balanced diet: Focus on whole foods, lean proteins, fruits, vegetables, and complex carbohydrates, and consider increasing energy intake by 300-600 kcal/day to address low energy availability, as suggested by the IOC consensus statement 1.
  • Stay hydrated: Drink at least 8 glasses of water daily.
  • Manage stress: Practice relaxation techniques like meditation or deep breathing.
  • Consider supplements: Consult a doctor about vitamin B12, iron, or magnesium supplements if deficient, as low energy availability can lead to nutrient deficiencies, as discussed in the 2014 Female Athlete Triad Coalition Consensus Statement 4. If symptoms persist, consult a healthcare provider to rule out underlying medical conditions such as thyroid disorders, anemia, or depression, which can contribute to low energy states, as highlighted in the IOC consensus statement on RED-S 2, 3. The most effective approach to addressing low energy states is to increase energy intake and reduce energy expenditure, while also addressing underlying lifestyle factors, nutrient deficiencies, and hormonal imbalances, as emphasized in the IOC consensus statement on RED-S 1, 2, 3.

From the Research

Definition of Low Energy

  • A state of low energy, also known as fatigue or lethargy, is characterized by a lack of energy to support physiological functions needed to maintain optimal health 5.
  • This condition can result from insufficient caloric intake to support exercise energy expenditure, leading to compromised physiological processes 6.

Causes of Low Energy

  • Low energy availability (LEA) can be caused by altered dietary behaviors, body dissatisfaction, social pressure to look a certain way, and high energy expenditure in sports such as rowing or cycling 5.
  • LEA can also be caused by an imbalance between energy expenditure from athletic training and bodily functions, and caloric intake 7.

Consequences of Low Energy

  • Low energy availability can have detrimental consequences on health and performance, including endocrine alterations, suppression of the reproductive axis, mental disorders, thyroid suppression, and altered metabolic responses 5.
  • LEA can also lead to impaired bone health, increased risk of bone stress injuries, and decreased athletic performance, including run performance, training response, endurance performance, coordination, concentration, judgment, explosive power, and agility 7.

Prevalence of Low Energy

  • The prevalence of LEA among athletes is estimated to be around 44.7%, with 44.2% of female athletes and 49.4% of male athletes affected 7.
  • The prevalence of relative energy deficiency in sport (REDs) is estimated to be around 63.0% among athletes with LEA 7.

Professional Medical Disclaimer

This information is intended for healthcare professionals. Any medical decision-making should rely on clinical judgment and independently verified information. The content provided herein does not replace professional discretion and should be considered supplementary to established clinical guidelines. Healthcare providers should verify all information against primary literature and current practice standards before application in patient care. Dr.Oracle assumes no liability for clinical decisions based on this content.