What Will Happen If You Don't Have Food? The Critical Effects of Starvation

December 23, 2025 •

2 min read

Hundreds of millions worldwide face undernutrition, which is a major contributor to mortality, especially in children. Understanding what will happen if you don't have food reveals the body's desperate survival mechanisms and the severe, cascading health crises that follow.

Quick Summary

Without food, the body enters a starvation state, systematically breaking down stored glycogen, then fat, and finally muscle tissue for energy. This leads to severe physical and psychological degradation, systemic organ damage, and can be fatal.

Key Points

Initial Response: The body first consumes available glucose, then stored glycogen in the liver and muscles within the first 24 hours.
Ketosis Phase: After the first day, the body starts breaking down fat stores to produce ketones for energy, a phase that can last for weeks.
Protein Breakdown: Once fat is gone, the body consumes its own muscle tissue, including the heart, leading to severe weakness and organ failure.
Psychological Impact: Starvation profoundly affects mental health, causing anxiety, depression, obsessive food thoughts, and cognitive impairment.
Refeeding Syndrome: Reintroducing food too quickly after prolonged starvation can cause a dangerous and potentially fatal electrolyte imbalance known as refeeding syndrome.
Survival Factors: Survival time is highly dependent on factors like initial body fat, hydration levels (which can extend survival significantly), and overall health.
Long-term Effects: Surviving starvation can lead to lasting health problems, including osteoporosis, infertility, heart conditions, and psychological disorders.

The Body's Survival Plan: A Staged Response to Starvation

When food is unavailable, the human body enacts a multi-phase survival strategy using stored energy. The timeline and severity depend on individual factors like initial body fat, hydration, age, and health.

Stage 1: The Initial Fast (6–24 hours)

Initially, the body uses blood glucose and liver/muscle glycogen stores. Symptoms like fatigue, irritability, and hunger may occur as blood sugar drops.

Stage 2: The Fat-Burning Phase (1–3 weeks)

After glycogen is depleted, the body burns fat for energy, producing ketones. This leads to weight loss and symptoms such as brain fog and headaches.

Stage 3: The Protein Cannibalization (Beyond 3 weeks)

Once fat stores are exhausted, the body breaks down muscle tissue for energy. This severe stage causes extreme weakness and organ failure, including compromised heart function.

Comparison of Energy Sources During Starvation


Stage	Duration	Primary Energy Source	Secondary Energy Source	Effects and Symptoms
1: Initial Fast	Up to 24 hours	Blood Glucose	Stored Glycogen	Fatigue, irritability, hunger pangs, low blood sugar
2: Ketosis	Days to weeks	Stored Fat (Ketones)	Remaining Glucose	Significant weight loss, brain fog, headaches, persistent fatigue
3: Protein Breakdown	3+ weeks	Muscle Tissue (Protein)	N/A	Severe muscle wasting, organ failure, extreme weakness, heart damage

Comprehensive Health Consequences of Food Deprivation

Starvation impacts nearly every body system.

Physical Degradation

Organ Damage: Leads to systemic failure of organs like the heart, kidneys, and liver.
Weakened Immunity: Nutrient deficiencies impair the immune system, increasing infection risk.
Cardiovascular Issues: Low blood pressure, slow heart rate, and heart failure are risks as heart muscle is used for energy.
Gastrointestinal Problems: Weakened digestive muscles cause bloating, constipation, or diarrhea.
Reproductive Disturbances: Hormonal imbalances can cause amenorrhea and decreased testosterone.
Bone Health: Lack of nutrition reduces bone density, increasing fracture risk.

Psychological and Cognitive Decline

Starvation severely affects mental health, as documented by studies like Ancel Keys'.

Mood Fluctuations: Leads to anxiety, depression, apathy, and irritability.
Cognitive Impairment: Causes difficulty concentrating, poor memory, and impaired judgment due to lack of brain fuel.
Food Preoccupation: Results in obsessive thoughts about food.
Personality Changes: Can lead to social withdrawal and emotional numbness.

The Dangers of Refeeding

Rapidly reintroducing food after prolonged starvation can trigger refeeding syndrome, a dangerous condition caused by electrolyte shifts. This can lead to serious complications including muscle cramps, respiratory failure, fluid retention, cardiac arrhythmias, and neurological issues. Refeeding requires gradual, medical supervision.

Conclusion: Starvation is Not a Survival Strategy

What will happen if you don't have food is a dangerous process of bodily decline, not a safe method for weight loss. While the body attempts to survive by consuming its own tissues, this is unsustainable and leads to severe, potentially irreversible damage affecting physical, mental, and emotional health. Recovery requires careful medical intervention, particularly during the refeeding phase, to prevent complications. More information on malnutrition is available from the World Health Organization: WHO Fact Sheet on Malnutrition

Frequently Asked Questions

While the exact time varies based on individual factors like body fat and health, and assuming adequate water intake, a person can survive for approximately one to two months without food. Without water, survival is limited to a matter of days.

Refeeding syndrome is a potentially fatal condition that can occur when a severely malnourished person is fed too quickly. It causes dangerous fluid and electrolyte shifts that can affect organ systems, particularly the heart.

Yes, prolonged food deprivation can have severe psychological and cognitive effects, including anxiety, depression, apathy, and impaired concentration. These are often due to a lack of proper nutrients to fuel the brain.

The body first consumes glucose and stored glycogen. After these are depleted, it burns fat to produce ketones. In the final stage of starvation, it begins to break down protein from muscle tissue.

As starvation progresses and the body begins to break down muscle for energy, the heart muscle can be compromised. This leads to a slowed heart rate, low blood pressure, and an increased risk of heart failure.

Yes, individuals who experience prolonged starvation can suffer long-term health consequences, such as stunted growth, compromised bone health, persistent mental health issues like PTSD or depression, and permanent organ damage.

Medical supervision is crucial to manage the risks of refeeding syndrome and ensure a slow, controlled reintroduction of nutrients. This helps prevent dangerous electrolyte imbalances and allows the body to safely rebuild its reserves.