15 warning signs that indicate you’re not getting enough calories for your workouts

Just as the low fuel light on a car’s dashboard lights up when the tank is nearly empty, our bodies send internal warnings when we are low on energy. However, these signals are not so obvious. If your diet doesn’t support the energy expenditure of your workouts, there can be serious consequences: hormonal imbalances, weakened immunity, slower metabolism, and an increased risk of injury.

Contents of the article:

• 15 signs that indicate a lack of energy for
  • 1. Frequent mood swings, irritability and loss of energy
  • 2. Constant thoughts about food and difficulties with choosing foods
  • 3. Uncontrollable bouts of overeating in the afternoon
  • 4. Exercises became harder
  • 5. Prolonged fatigue after sports
  • 6. Loss of desire to exercise
  • 7. Sleep quality problems
  • 8. Digestive problems
  • 9. Hormonal disorders
  • 10. Decreased sex drive
  • 11. Slow heart rate and increased cholesterol levels
  • 12. Unpredictable weight gain
  • 13. Constantly feeling cold
  • 14. Skin and hair disorders
  • 15. Increased likelihood of injury

this condition is called low energy availability, which can develop into a relative energy deficiency affecting almost all body systems. According to a study published in the British Journal of Sports Medicine in 2024, signs of low energy availability were found in 42% of women and 17% of men who took part in the Boston Marathon.

15 signs that indicate a lack of energy for effective training

1. Frequent mood swings, irritability and loss of energy

If you notice frequent irritability, sudden emotional swings, or a constant feeling of apathy, this may not only be caused by stress. A study published in the Journal of Clinical Psychology in 2023 found that a lack of calories reduces serotonin and dopamine levels, which directly affects psycho-emotional state.

Hunger is often expressed through moodiness, irritability and bad mood.

• What to do? Increase your caloric intake with complex carbohydrates, healthy fats and a balanced amount of protein.

2. Constant thoughts about food and difficulties with choosing foods

When the body does not receive enough nutrition, the mind tends to focus on food. An obsessive desire to eat and difficulties with what to choose may indicate an inadequate diet and energy deficiency. Disturbances in the functioning of the hypothalamus due to lack of feeding make it difficult to correctly perceive hunger signals.

• What to do? Think over your diet in advance, include all the necessary macro- and micronutrients.

3. Uncontrollable bouts of overeating in the afternoon

A lack of calories can start a vicious circle: skimping on breakfast and lunch leads to severe hunger in the evening, which provokes gluttony. After this, a feeling of guilt arises, and you again begin to limit yourself, repeating the cycle again. If you provide the body with the necessary calories and distribute meals evenly, the feeling of hunger will not go to extremes.

• What to do? Distribute meals evenly, adding snacks with protein and fiber if necessary.

4. Exercises became harder

Your energy level during a workout depends on many factors: preparation from the previous day, quality of sleep, stress at work, etc. However, if previously 5 kilometers of running were easy, but now every exercise causes fatigue, your body probably doesn’t have enough carbohydrates to restore glycogen stores.

• What to do? Add carbohydrates before and after workouts, such as a banana or oatmeal.

5. Prolonged fatigue after sports

Serious training, such as training for a half marathon, causes fatigue. However, with adequate nutrition and a gradual increase in exercise, you should not feel a loss of strength for several days. If after training you experience complete exhaustion, this may indicate insufficient calorie intake.

• What will be useful? Provide your body with recovery protein, such as Greek yogurt with berries or a protein shake.

6. Loss of desire to exercise

Whether you’re preparing for a competition or training to improve your well-being, decreased motivation happens to everyone sometimes. However, if activities that were previously enjoyable suddenly become less enjoyable and you are tempted to skip a few training , the cause may be chronic energy deficiency.

• What to do? Include more healthy fats in your diet, which support hormonal levels and the nervous system.

7. Sleep quality problems

Hunger and lack of calories can lead to overwork, but at the same time, sleep becomes shallow and often interrupted. Falling blood sugar levels can cause nighttime awakenings, and deficiencies in essential nutrients impair sleep quality, making you feel more tired when you wake up.

• What to do? Eat carbohydrates before bed, for example, warm milk with honey, 2-3 hours before bedtime.

8. Digestive problems

Not getting enough calories can negatively impact your gastrointestinal tract, causing pain, bloating, constipation, or diarrhea—symptoms similar to irritable bowel syndrome. Often people begin to eliminate certain food groups from their diet, such as dairy or gluten, without adding alternative nutritional sources, which worsens energy deficits.

• What to do? Control the balance of proteins, fats and carbohydrates in your diet.

9. Hormonal disorders

Blood tests can reveal deficiencies in vitamins and minerals obtained from food. Insufficient intake of key nutrients reduces the absorption of important elements. In women, this can be manifested by menstrual irregularities, in men – by a decrease in testosterone. A calorie deficit causes the body to release hepcidin, which interferes with the absorption of iron, causing iron levels in the blood to deteriorate. Tests may also show abnormalities in the levels of thyroid hormones – thyroid-stimulating hormone (TSH) and free T3, which are sometimes mistaken for thyroid disease, although the reason lies in poor nutrition affecting the pituitary gland.

• What to do? Provide your diet with foods rich in calcium, potassium and iron.

10. Decreased sex drive

Decreased secretion of estrogen and testosterone due to energy deficiency can lead to a drop in libido, exacerbating irritability and complicating relationships with a partner. The body conserves resources to function in everyday life, and women especially react sensitively to a lack of calories, which affects hormonal balance.

• What to do? Include more foods rich in zinc and vitamin D in your diet.

11. Slow heart rate and increased cholesterol levels

Athletes typically have a lower resting heart rate than normal, but too few calories further slow the heart. With nutritional deficiency, metabolism slows down, which leads to an increase in “harmful” food. cholesterol.

• What to do? Add healthy fats and proteins to your diet.

12. Unpredictable weight gain

It is believed that reducing calories automatically leads to weight loss. However, for some people, body weight may increase when calorie restriction occurs due to a slower metabolism and the body’s attempts to conserve energy.

• What to do? Pay attention to the correct balance of macronutrients and an even distribution of calories across meals.

13. Constantly feeling cold

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Raynaud’s syndrome is a pathological condition in which vascular spasms cause numbness in the limbs and other parts of the body. Symptoms are significantly aggravated by insufficient calorie intake, since energy deficiency can negatively affect the functioning of blood vessels. In addition, an imbalanced thyroid hormone may cause you to feel unusually cold. Decreased levels of the T3 hormone lead to a decrease in body temperature in order to conserve the energy needed to maintain warm blood. This is why people who radically limit their diet often feel constantly cold.

• Recommendation: Include more complex carbohydrates and healthy fats in your diet.

14. Skin and hair disorders

Hormonal fluctuations, deficiency of important microelements and proteins can negatively affect the condition of the skin and hair. Many people experience hair loss or thinning, their skin condition worsens, and their nails become prone to brittleness. However, given the seriousness of this problem, taking biotin in any quantity will not solve the situation.

• Recommendation: Increase the amount of protein in your diet, as well as vitamins A and E.

15. Increased likelihood of injury

Bone damage is closely associated with poor diet and eating disorders, especially in women. Lack of calcium and vitamin D, which are essential for strong bones, along with low energy levels, can lead to hormonal shifts that weaken bones and increase the risk of injuries such as stress fractures.

• Recommendation: Monitor and maintain adequate calcium and vitamin D levels.