What will happen if we don't get food? Understanding starvation

January 2, 2026 •

4 min read

According to the World Health Organization, malnutrition is a significant contributor to child mortality, and millions face food insecurity every year. But what will happen if we don't get food? The journey from simple hunger to life-threatening starvation involves a complex sequence of physical and mental changes as the body desperately tries to conserve energy and find alternative fuel sources from its own reserves.

Quick Summary

Without food, the human body undergoes a series of metabolic stages to survive, breaking down stored glycogen, then fat, and finally muscle and organ tissue. This process leads to severe physical and psychological consequences, including cognitive impairment, a weakened immune system, organ failure, and eventually death.

Key Points

Three-Phase Process: The body first burns stored glycogen for up to 24 hours, then shifts to fat metabolism (ketosis) for weeks, and finally resorts to breaking down muscle and organ tissue (protein wasting).
Vital Organ Damage: In the final stage of starvation, the body consumes its own organs, including the heart, leading to organ failure and cardiac arrest.
Immune System Collapse: Severe malnutrition causes the immune system to fail, making a starving person highly vulnerable to infections, which are often the ultimate cause of death.
Profound Psychological Toll: Starvation affects mental health, leading to anxiety, depression, apathy, irritability, and impaired cognitive function.
Refeeding Syndrome Risk: Reintroducing food too quickly after prolonged starvation can be fatal due to dangerous electrolyte shifts, a condition known as refeeding syndrome.
Survival Timeline Varies: The duration a person can survive without food depends on factors like starting body fat, age, and health status, but it is typically a matter of weeks, not months, for most individuals.

The Body's Survival Mechanism: A Three-Phase Process

When faced with a lack of food, the human body doesn't simply shut down. Instead, it activates a series of metabolic defense mechanisms to prolong survival. This process can be broken down into three distinct phases, each with its own set of physiological changes.

Phase 1: Glycogen Depletion (0-24 Hours)

Within the first day of not eating, the body's primary energy source comes from glucose stored in the liver in the form of glycogen. This stored glucose is readily converted back into energy to fuel the brain and muscles. Once these glycogen reserves are depleted, typically within about 24 hours, the body must find a new source of fuel to maintain vital functions.

Phase 2: Fat Metabolism (Day 2 - Several Weeks)

After exhausting its glycogen stores, the body begins breaking down stored fats. The liver converts these fats into ketone bodies, which can be used by the brain and other tissues for energy. This process, known as ketosis, allows the body to conserve muscle mass for as long as possible. The duration of this phase depends heavily on an individual's body fat reserves; leaner people will progress to the next phase much faster than those with more fat. During this time, symptoms like fatigue, headaches, and impaired concentration can begin to manifest.

Phase 3: Protein Breakdown (Weeks 3 and Beyond)

Once fat stores are gone, the body enters a critical and highly dangerous stage where it begins catabolizing protein from muscle tissue for energy. This phase, known as protein wasting, leads to severe muscle atrophy and extreme weakness. The breakdown includes vital organs like the heart, which is primarily muscle tissue. The immune system collapses, leaving the body highly susceptible to infection, which is often the direct cause of death in cases of prolonged starvation.

Long-Term Physical and Psychological Consequences

The effects of prolonged starvation extend far beyond simple weight loss, leaving lasting damage to both the body and mind. The famous Minnesota Starvation Experiment, conducted in the 1940s, provided deep insight into the profound physical and psychological toll of semi-starvation, with subjects exhibiting dramatic changes that persisted even after re-feeding.

Physical Degradation

Organ shrinkage: As the body breaks down protein for energy, vital organs like the heart, liver, and kidneys shrink and their function deteriorates.
Circulatory issues: Heart rate and blood pressure drop significantly, increasing the risk of cardiac arrhythmia and heart failure.
Immune system failure: Severe vitamin and mineral deficiencies cripple the immune system, making infections like pneumonia a common cause of death.
Edema: Massive fluid retention and swelling, known as edema, can occur in the limbs and abdomen due to protein deficiency, a condition known as Kwashiorkor in severe childhood malnutrition.

Psychological and Behavioral Changes

Cognitive decline: Impaired concentration, alertness, and judgment are common as the brain receives less fuel. In severe cases, psychosis, delusions, and amnesia can occur.
Mood and personality shifts: Irritability, apathy, anxiety, and depression are prevalent. The preoccupation with food can become intense, consuming thoughts and dreams.
Social withdrawal: Individuals become more introverted and socially isolated, with a marked reduction in social initiative and desire for human contact.

Starvation vs. Fasting: A Comparison


Feature	Starvation	Therapeutic Fasting
Duration	Prolonged, often weeks or months.	Short-term, usually hours or a few days.
Context	Involuntary, due to famine, crisis, or illness.	Voluntary, for health or religious reasons.
Body's Response	Phase 3: Catabolizes vital muscle/organ tissue after fat reserves deplete.	Phase 1-2: Utilizes glycogen and fat stores, does not typically progress to muscle breakdown.
Health Outcome	Leads to severe malnutrition, permanent organ damage, and death.	Generally safe under medical supervision for limited durations.
Refeeding	Dangerous process requiring cautious, slow reintroduction of food (Refeeding Syndrome).	Normal re-feeding can resume safely for most people.

The Dangers of Refeeding

Paradoxically, the process of reintroducing food to a severely malnourished individual can be fatal if not managed carefully. This condition, known as refeeding syndrome, occurs when food is reintroduced too quickly after a period of starvation. It can cause sudden and dangerous shifts in fluid and electrolyte levels, leading to serious complications like heart failure, seizures, and respiratory distress. For this reason, medical professionals must manage the re-feeding process slowly and with close monitoring.

Conclusion

If we don't get food, the human body's initial resilience gives way to a desperate process of consuming its own tissues. The sequence moves from burning readily available glucose to metabolizing fat and, finally, breaking down vital muscle and organ proteins. The consequences are dire, involving severe physical degradation, profound psychological distress, and a complete collapse of the immune system. Survival is a multi-stage race against time, and once the body begins consuming itself, the long-term outlook is grim. Understanding this critical biological process underscores the essential role of food for human life and the catastrophic reality of global hunger crises.

[Authoritative link example]: What is Refeeding Syndrome?

Frequently Asked Questions

While survival time varies based on factors like initial body fat, hydration levels, age, and health, most estimates suggest an average person can survive for approximately two to three weeks without food, provided they have access to water.

Yes, during the final and most dangerous phase of starvation, after exhausting its fat reserves, the body breaks down its own muscle and vital organ tissue for energy, a process known as protein catabolism.

Within 24 hours of ceasing food intake, the body primarily uses up its stored glucose (glycogen) from the liver to maintain energy levels for the brain and other tissues.

Psychological effects of starvation include anxiety, irritability, apathy, depression, and obsessive thoughts about food. Concentration and decision-making skills also become severely impaired.

Yes, although a person with higher fat reserves might survive longer, the ultimate cause of death from starvation is often organ failure or infection, which can happen after the body's fat and protein stores are depleted.

Refeeding syndrome is a potentially fatal condition that occurs when food is reintroduced too rapidly after prolonged starvation, causing sudden and dangerous shifts in fluids and electrolytes in the body.

A bloated stomach, or edema, is a symptom of severe protein deficiency, a condition called Kwashiorkor. It causes fluid retention and swelling, particularly in the limbs and abdomen.

No. Fasting is a voluntary, short-term abstinence from food that typically does not last long enough to enter the final, dangerous stage of protein breakdown. Starvation is a prolonged, involuntary deficiency that leads to severe health consequences.