Feeling hungry can have a variety of causes and understanding them can help you better manage your eating. Some common reasons why you might feel hungry are your own physiological needs, a lack of hydration, emotional factors, or what I see most often in consultation, low blood glucose levels.

Glucose is a type of simple sugar that serves as the main source of energy for many cells in the body. It is a monosaccharide, which means it is a sugar molecule made up of only one type of sugar unit. Glucose is essential for the proper functioning of the human body, providing the energy needed to carry out various cellular and metabolic functions. When this glucose is low in the blood, our body wants to increase it for energy.

When you eat foods containing carbohydrates, such as sugars and starches, your body breaks these compounds down into glucose during digestion. Glucose then circulates in the bloodstream and is transported to cells for immediate use as an energy source or stored in the liver and muscles as glycogen for future use.

Careful regulation of blood glucose levels is crucial to maintaining health. The hormone insulin, produced by the pancreas, plays a key role in this process, facilitating the entry of glucose into cells and helping to keep blood glucose levels within a normal range. Problems in glucose regulation, such as diabetes, can have significant health consequences.

When does blood glucose rise or fall?

Blood glucose tends to rise and fall in response to various factors, and we need to understand and be aware that this is a normal process in the body. Here are some common situations in which blood glucose levels may fluctuate:

  • After Eating (Postprandial): After a meal, blood glucose levels tend to rise due to the absorption of glucose from food in the digestive system. This is part of the body's natural response to food intake. However, an unbalanced meal will lead to dysregulation of these glucose levels and make us hungry earlier than normal.
  • Fasting or Prolonged No Food Period: During fasting or if too much time passes between meals, blood glucose levels may drop as the body uses stored glucose for energy.
  • Exercise: Physical activity can lower blood glucose levels as muscles use glucose as a source of energy during exercise.
  • Stress: Stress can affect blood glucose levels. In stressful situations, the body may release hormones that increase glucose levels to provide additional energy.
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How do fluctuations in blood glucose levels affect our bodies?

Fluctuations in blood glucose levels can have diverse effects on the body and health, especially if these fluctuations are extreme or occur frequently. Here are some ways in which fluctuations in glucose levels can affect us:

Fatigue and Energy:

Low blood glucose levels can lead to fatigue and weakness, as cells do not receive enough energy to function properly.

High glucose levels can cause fatigue due to insulin resistance, where cells have difficulty using the available glucose.

These continual rises and falls in blood glucose will cause our bodies to experience momentary energy spikes and continuous spikes of extreme fatigue. This is something that many people think is normal on a day-to-day basis, but it is not. Maintaining regular blood glucose levels will also keep our energy stable.

Mood swings:

Swings in glucose levels can affect our mood. Low glucose levels can cause irritability and mood swings, while high levels can be associated with fatigue and lethargy. When we are in a low, listless state, we seek out foods that make us feel better, usually sweets, which will cause these glucose levels to rise rapidly.

Cognitive problems:

Low glucose levels can affect brain function and concentration. This is especially important because the brain relies heavily on glucose as an energy source. People with attention deficit disorder, autism, or other cognitive pathologies, maintaining regular glucose levels will prevent these problems from being exaggerated.

Physical symptoms:

Extreme swings can cause physical symptoms such as tremors, sweating, dizziness, and in more severe cases, fainting.

Organ and Tissue Damage:

Long-term elevated glucose levels, as in the case of poorly controlled diabetes, can contribute to organ and tissue damage, including the eyes, kidneys, nerves and blood vessels.

Increased Cardiovascular Risk:

Frequent fluctuations in glucose levels, especially if extreme, can increase the risk of cardiovascular disease.

Metabolic Problems:

Frequent swings can contribute to insulin resistance, which can lead to the development of type 2 diabetes.

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What can we do to avoid glucose swings and keep hunger controlled?

If we start our day with a breakfast high in refined carbohydrates (white bread, pastries, biscuits or even cereals coming from a box) or even orange juice, our blood glucose will shoot up first thing in the morning. This will lead to a consequent drop in blood sugar and therefore an increase in appetite mid-morning (sounds familiar, doesn’t it?). Our body is wise, and once it gets that glucose spike first thing in the morning, it will always look for you to keep it that high, but it’s not healthy.

Keeping hunger at bay means adopting eating and lifestyle habits that help control your appetite. Here are some strategies that can help you keep hunger under control:

  • Eat Balanced Meals: Include lean protein, complex carbohydrates and healthy fats at every meal. These nutrients provide a feeling of satiety and help keep energy levels stable. Follow the Harvard Plate for lunch and dinner, adjusting proportions to your physical activity, weight, height and goals.
  • Eat Fibre: Fibre-rich foods, such as fruits, vegetables, whole grains and legumes, are more satisfying and can help keep hunger at bay by increasing satiety.
  • Adequate Hydration: Sometimes, thirst can be mistaken for hunger. Drinking enough water throughout the day can help keep hunger under control.
  • Avoid Refined Sugars and Carbohydrates: Foods high in simple sugars and refined carbohydrates can lead to fluctuations in blood glucose levels, which can increase appetite. Go for healthier sources of carbohydrates.
  • Include Healthy Snacks: It's OK if you feel hungry between meals, choose healthy and satiating snacks, such as fruit, Greek yoghurt, nuts or veggies with hummus.
  • Get Enough Sleep: Lack of sleep can affect the hormones that regulate hunger and appetite. Try to make sure you get enough sleep each night.
  • Manage Stress: Stress can affect appetite. Practicing stress management techniques, such as meditation or yoga, can help control emotional hunger.
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Remember that everyone is unique, and it can be helpful to experiment with different approaches to find what works best for you. A healthy eating pattern involves eating 3 times a day, 5 times a day or even 2 times a day. However, if you experience a constant and unusual feeling of hunger, or if there are significant changes in your appetite with no obvious cause, it may be helpful to consult a nutritionist for personalised guidance.

About the author

Adriana Martín is a clinical nutritionist at Sinews. She treats adults, adolescents and children seeking to improve their health through nutrition. She specialises in public health and also treats TCA, SIBO, chronic diseases and other pathologies, as well as muscle mass gain or weight loss. Her approach is not to prescribe closed menus, but to make people understand the importance of nutrition at every stage of life through different tools.

Adriana Martín Peral
División of Nutrition
Adriana Martín Peral
Children, adolescents and adults
Languages: English and Spanish
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