What Will Happen If You Only Drink Water and No Food?: The Dangers of Prolonged Fasting

October 29, 2025 •

4 min read

Records exist of individuals surviving for over 70 days with water alone, but doing so carries severe, life-threatening risks. This metabolic adaptation, known as starvation, is the definitive answer to the question: 'what will happen if you only drink water and no food?'. While the body is resilient, prolonged abstinence from food ultimately leads to severe health decline and, eventually, organ failure.

Quick Summary

The body shifts from burning glucose to relying on fat stores, a process known as ketosis, when deprived of food. As fat reserves are depleted, the body begins to break down muscle tissue for energy, leading to severe physical and cognitive deterioration, and ultimately, death.

Key Points

Initial Fuel Depletion: Within the first 24-48 hours of consuming only water, the body uses up its stored glycogen for energy, leading to initial fatigue and hunger.
Ketosis and Fat Burning: After glycogen is depleted, the body enters ketosis, burning stored fat for fuel. This phase can last weeks, but often involves significant water and muscle loss, not just fat.
Dangerous Protein Wasting: Once fat stores are gone, the body turns to vital muscle tissue, including the heart, for energy. This is the most dangerous stage of starvation and can lead to organ failure.
Electrolyte Imbalance: A lack of food and nutrients can disrupt the balance of crucial electrolytes like sodium and potassium, potentially causing fatal cardiac problems.
Refeeding Syndrome Risk: Reintroducing food too quickly after prolonged starvation can trigger a fatal electrolyte shift, making medical supervision essential during recovery.
Psychological and Cognitive Effects: Starvation impairs mental function, causes emotional instability, and results in a debilitating preoccupation with food.
Not Recommended for Self-Practice: A prolonged water-only diet is extremely dangerous and should never be attempted without strict medical guidance due to the severe risks of malnutrition, organ damage, and death.

The human body is a resilient, finely tuned machine designed for survival. When food intake is restricted, it initiates a series of metabolic processes to sustain life for as long as possible. However, this is not a sustainable state and a water-only diet without proper medical supervision is extremely dangerous and can be fatal.

The Three Stages of Starvation

Understanding the body's response to no food is best viewed in distinct phases. The duration of each stage can vary significantly based on an individual's starting health, age, body fat percentage, and activity levels.

Phase 1: Glycogen Depletion (First 24-48 Hours)

After eating, the body primarily uses glucose from food for energy. Without a new supply, it turns to its stored form of glucose, known as glycogen, located in the liver and muscles. This reserve is quickly depleted, usually within 24 to 48 hours.

Symptoms: During this initial phase, a person will experience common signs of hunger, such as fatigue, irritability, and headache, as the body's primary fuel source runs out.
Metabolic Shift: Once glycogen is gone, the body begins shifting towards fat and protein for energy.

Phase 2: Ketosis (From Day 2-3 to Several Weeks)

As the body's glycogen stores are depleted, it enters ketosis, a state where it primarily burns stored fat for energy. The liver converts fatty acids into ketone bodies, which can be used by most tissues, including the brain. This phase can last for weeks, depending on the individual's body fat reserves.

Weight Loss: Rapid weight loss occurs, with a significant portion being water weight and lost muscle mass, not just fat.
Mental Effects: Initial feelings of improved energy and clarity, as some studies suggest, may give way to apathy and emotional changes.
Dangers: A key danger during this phase is dehydration, as some daily water intake comes from food. Electrolyte imbalances can also occur, which can be life-threatening.

Phase 3: Protein Wasting (After Fat Stores Deplete)

This is the most critical and life-threatening phase of starvation. Once fat reserves are largely exhausted, the body begins breaking down muscle tissue and other proteins to meet its energy needs. This includes the crucial protein in vital organs, such as the heart.

Severe Symptoms: Severe symptoms emerge, including extreme weakness, organ failure, weakened immune function, and severe cognitive impairment.
Fatal Consequences: Death from prolonged starvation is often the result of cardiac arrhythmia, infection due to a compromised immune system, or multi-organ failure.

Comparison: Short-Term Water Fasting vs. Prolonged Starvation

While some individuals may undertake short-term water fasts (24-72 hours) under medical supervision for specific therapeutic reasons, this is vastly different from prolonged starvation.


Feature	Short-Term Water Fasting (24-72 hours)	Prolonged Starvation (Weeks+)
Primary Fuel Source	Glycogen, then shifts to stored fat.	Stored fat initially, then shifts to vital muscle tissue.
Health Impact	Minor side effects like headaches, dizziness, and fatigue are common.	Severe, cumulative damage to organs, bone density, and immune function.
Medical Oversight	Often recommended or required, especially for individuals with underlying conditions.	Critical and ongoing medical management is necessary; not a lifestyle choice.
Risks	Dehydration and electrolyte shifts are possible but usually manageable.	Refeeding syndrome and death from organ failure are significant risks.
Metabolic State	Controlled ketosis, with body largely conserving protein.	Widespread protein wasting, leading to catastrophic organ damage.

The Unhealthy Consequences of a Water-Only Diet

A decision to restrict food intake to only water, especially without a doctor's oversight, invites a host of severe health complications.

Nutrient Deficiency: The body cannot produce essential nutrients like vitamins, minerals, and essential fatty acids. Prolonged deficiency can lead to anemia, neurological issues, bone density loss, and skin problems.
Electrolyte Imbalances: A lack of food and nutrients can cause critical changes in blood electrolytes like sodium and potassium, which regulate nerve and muscle function, including the heart. Severe imbalances can cause arrhythmia or cardiac arrest.
Orthostatic Hypotension: This is a sudden drop in blood pressure when standing up, caused by dehydration and metabolic changes. It can lead to dizziness, lightheadedness, and fainting.
Muscle Atrophy: Eventually, the body consumes its own muscle tissue for energy. The heart, as a muscle, is particularly at risk.
Refeeding Syndrome: This potentially fatal condition occurs when a severely malnourished person is fed too quickly after prolonged starvation. It causes a rapid and dangerous shift in fluids and electrolytes.

For more information on the dangers and requirements of specific fasting protocols, a resource like Healthline provides a comprehensive overview of safety considerations.

The Psychological and Cognitive Toll

In addition to the physical dangers, starvation profoundly affects mental and emotional health. Studies, such as the Minnesota Starvation Experiment, have documented significant psychological changes.

Cognitive Decline: Impaired concentration, judgment, and overall cognitive function are common. The brain shifts from its preferred fuel, glucose, to less efficient ketone bodies, impacting its performance.
Emotional Instability: Irritability, anxiety, and depression are frequently observed. Apathy and social withdrawal can also occur as the body conserves energy.
Food Preoccupation: A heightened, obsessive preoccupation with food becomes a central focus of thoughts, daydreams, and behavior.

Conclusion: A Dangerous Path

While the human body is capable of surviving for weeks without food with adequate water, this is not a healthy or sustainable practice. Prolonged water-only diets cause the body to enter a state of starvation, leading to a cascade of dangerous metabolic shifts, severe nutritional deficiencies, and organ damage. Any form of extended fasting should only be considered under strict medical supervision. The quick weight loss that may occur initially is often water and muscle mass, not fat, and the risks of long-term starvation are potentially irreversible and fatal.

Disclaimer: This article is for informational purposes only and does not constitute medical advice. Anyone considering a water fast or experiencing starvation symptoms should consult a healthcare professional immediately.

Frequently Asked Questions

While estimates vary based on individual factors like starting body fat and health, survival on water alone can potentially extend up to two to three months, although this comes with severe health risks and deterioration.

In the first couple of days, immediate side effects include fatigue, headaches, dizziness, irritability, and intense hunger, primarily due to low blood sugar as glycogen stores are used up.

Water fasting, especially for more than 24-72 hours, is not recommended as a safe weight-loss method without medical supervision. It can lead to rapid weight loss from water and muscle, not just fat, and carries risks like dehydration and electrolyte imbalances.

Yes, paradoxically, drinking only water can cause dehydration. A significant portion of daily water intake typically comes from solid food, so abstaining from food can dramatically reduce internal water levels, despite drinking water.

During prolonged water-only fasting, once fat stores are largely depleted, the body begins to break down its own muscle tissue for energy. This is a critical stage of starvation that leads to severe weakness and organ damage.

Refeeding syndrome is a potentially fatal condition caused by a rapid and dangerous shift in fluids and electrolytes when a severely malnourished person is re-fed too quickly. It can lead to heart conditions and neurological issues.

Starvation can severely affect the brain, leading to cognitive impairment, mood swings, irritability, depression, and an intense preoccupation with food. The brain's fuel source shifts from glucose to ketone bodies, impacting its function.