Many people have experienced the urge to have a snack suddenly, even if they recently ate a full meal. Often, we instinctively reach for food when, in fact, the body is signaling a lack of fluids. This common confusion between hunger and thirst has a scientific explanation and can lead to the development of unhealthy eating habits and a decline in well-being.
The reason for this phenomenon lies in the way our brain works. As explained by Andrea Azcárate Villalón, head of the endocrinology and nutrition department at Hospital Universitario Sanitas La Moraleja, the centers responsible for hunger and thirst are located in the hypothalamus, very close to each other. While they use different neural pathways to process signals, their proximity can sometimes cause misinterpretation. The brain receives a signal about a lack of water, but we perceive it as a call to eat, especially if we have not been drinking enough throughout the day.
Inadequate hydration can affect appetite in various ways. According to the specialist, in some cases, dehydration may actually decrease the desire to eat, particularly when accompanied by fatigue or headaches. In other situations, it can trigger a false sense of hunger, caused by general discomfort or the body’s subconscious drive to obtain moisture from juicy or salty foods.
The body sends early warning signals of impending dehydration to prevent the condition from worsening. Early signs include dry mouth, reduced urine output with darker color, feelings of fatigue and mild weakness. Other symptoms may include decreased concentration, headaches, and increased irritability. It is important to recognize these symptoms promptly and respond appropriately.
The consequences of insufficient water intake go far beyond physical discomfort. Even mild dehydration negatively impacts cognitive functions: short-term memory worsens, the ability to concentrate for extended periods declines, and thinking slows down. On an emotional level, this may manifest as unexplained anxiety, apathy, or irritability. The brain is highly sensitive to fluid balance, so these effects can occur rather quickly.
To distinguish between hunger and thirst, the expert suggests a simple and effective method. If you feel hungry, drink a glass of water and wait 15–20 minutes. If the sensation lessens or disappears, it was likely thirst. If it persists, you are probably genuinely hungry. Additional clues may come from accompanying symptoms: thirst often comes with a dry mouth, while hunger is typically marked by a feeling of emptiness in the stomach.
In cases where chronic dehydration is suspected, doctors turn to a comprehensive diagnostic approach. This includes reviewing the patient’s medical history, examining the skin and mucous membranes, as well as conducting laboratory tests. Specialists may measure plasma osmolality, sodium and urea levels in the blood, along with urine volume and concentration. In more complex situations, bioimpedance analysis and other methods are used to assess the body’s water balance.
