What Happens to the Body if You Only Drink Coffee?

October 10, 2025 •

3 min read

According to StatPearls, caffeine is the most commonly used psychoactive drug in the world, yet relying solely on coffee for sustenance can have devastating effects on the body. In fact, if you're wondering what happens to the body if you only drink coffee, the answer is a rapid descent into severe health crises, including malnutrition, dehydration, and significant psychological distress.

Quick Summary

A diet exclusively of coffee leads to severe malnutrition, dehydration, and a cascade of negative physical and mental health issues. Long-term dependence and serious organ damage are inevitable without proper nutrient and caloric intake.

Key Points

Nutrient Starvation: A coffee-only diet provides zero sustenance, leading to life-threatening malnutrition and lack of essential calories, proteins, and fats.
Severe Dehydration: Despite being a fluid, coffee's diuretic effect, especially at high intake, causes fluid and electrolyte loss, leading to dangerous dehydration and systemic stress.
Psychological Decline: Excessive caffeine intake and nutrient deprivation cause severe anxiety, chronic insomnia, irritability, and strong physical and psychological dependency.
Systemic Organ Damage: Prolonged malnutrition and dehydration affects every major organ, leading to an increased risk of heart damage, kidney failure, and osteoporosis.
Intensified Side Effects: Without food to buffer its effects, coffee on an empty stomach exacerbates issues like acid reflux and heartburn, and disrupts normal hormonal cycles.
Dangerous Dependence: Relying on caffeine leads to a cycle of needing more and more for the same effect, with severe withdrawal symptoms upon cessation.

The Illusion of Energy: Short-Term Effects

Upon starting a coffee-only regimen, the initial effects are centered on the stimulant properties of caffeine. The boost of energy and increased alertness is short-lived and comes with a host of unpleasant side effects. High doses of caffeine trigger the release of adrenaline and cortisol, the body's stress hormones, leading to an increased heart rate and blood pressure, jitters, and a feeling of anxiety. Additionally, caffeine can cause insomnia, which is a key contributor to fatigue and an over-reliance on coffee to stay awake.

For many, drinking coffee on an empty stomach—which would be a constant state in this diet—leads to significant gastrointestinal issues. Caffeine stimulates the secretion of gastric acid, and without food to buffer it, this can cause acid reflux, heartburn, and stomach irritation. The mild diuretic effect of caffeine also means that frequent urination leads to the loss of fluids and essential electrolytes, contributing to dehydration and a feeling of fatigue and dizziness.

The Nutritional Black Hole: Long-Term Consequences

Continuing with a coffee-only diet pushes the body into a state of chronic malnutrition. Coffee provides virtually no calories, protein, or fats—the fundamental building blocks for bodily functions. The body will begin to break down its own tissues for energy, leading to a dangerous loss of muscle mass. Eventually, a coffee-only diet becomes a pathway to starvation, with severe health consequences.

How Coffee Depletes Key Nutrients

Even beyond the lack of basic macronutrients, coffee actively interferes with the body's ability to absorb vital micronutrients. This nutritional deficiency is one of the most dangerous aspects of this extreme diet:

Calcium: Caffeine increases the excretion of calcium through urine, and chronic high intake can lead to lower bone mineral density and an increased risk of osteoporosis and fractures.
Iron: The polyphenols found in coffee can bind to non-heme iron, significantly reducing its absorption. This can lead to iron deficiency anemia, causing fatigue and weakness.
B Vitamins: The diuretic effect of caffeine depletes water-soluble vitamins like the B-vitamins. Heavy coffee consumption has been linked to lower levels of folate, vitamin B6, and riboflavin.
Magnesium and Zinc: Like iron, the absorption of magnesium and zinc is inhibited by coffee, and their excretion is increased by caffeine, leading to potential deficiencies.

Physiological and Psychological Fallout

The Body's Systemic Shutdown

As the body struggles with chronic nutrient and calorie deprivation, major organ systems begin to fail. The heart is particularly vulnerable, with excessive caffeine and electrolyte imbalances leading to an irregular heartbeat (arrhythmias). While moderate coffee intake has been linked to some liver and kidney benefits, severe dehydration and poor nutrition can override these, putting these organs under immense stress and risking long-term damage.

The Mental Health Toll

The psychological consequences of a coffee-only diet are just as severe as the physical ones. The high caffeine intake triggers and exacerbates anxiety, leading to a constant state of nervousness and agitation. Sleep becomes impossible, and the resulting chronic insomnia creates a feedback loop of anxiety and exhaustion. Over time, physical and psychological dependency on caffeine develops, and trying to stop would lead to severe withdrawal symptoms, including persistent headaches, fatigue, and depression.

A Comparison: All-Coffee 'Diet' vs. A Balanced Approach


Aspect	All-Coffee 'Diet'	Balanced Diet (with moderate coffee)
Energy Levels	High anxiety, followed by severe crashes	Stable energy, sustained focus
Nutrient Intake	Severe vitamin and mineral deficiencies	Diverse range of vitamins, minerals, macros
Mental Health	High anxiety, irritability, depression	Balanced mood, potential lower depression risk
Digestive Health	Acid reflux, stomach irritation, ulcers	Healthy gut flora, better digestion
Long-Term Risks	Starvation, organ damage, osteoporosis	Lower risk of certain diseases, overall health

Conclusion

Attempting to survive on a coffee-only diet is a dangerously unsustainable and life-threatening endeavor. While moderate coffee consumption can offer certain health benefits as part of a balanced lifestyle, using it as a sole source of nutrition is catastrophic for the body. The resulting malnutrition, dehydration, systemic organ damage, and psychological distress prove that coffee is a supplement to a healthy diet, not a substitute. For safe and sustainable wellness, it's essential to consume a variety of nutrients and rely on water as your primary source of hydration.

For more information on recommended caffeine intake and potential side effects, visit the Mayo Clinic.

Frequently Asked Questions

Yes, but this is a result of starvation and is extremely dangerous, not a healthy or sustainable method. The body breaks down tissue for energy, and the resulting health issues are severe. Weight regain is highly likely once normal eating resumes.

Survival would likely be a matter of weeks, similar to a person fasting on only water. The exact timeframe depends on individual factors like body fat and metabolism. Death would result from severe starvation and dehydration.

You would lack all macronutrients (carbohydrates, proteins, fats) and many micronutrients, as coffee is not a food source. Key deficiencies would include calcium, iron, magnesium, zinc, and B vitamins, among others.

While coffee contains water, heavy or excessive consumption can contribute to dehydration due to its diuretic effect, which causes you to urinate more frequently and lose electrolytes.

Occasionally replacing a meal with coffee is not advisable and can lead to issues like acid reflux. Drinking coffee on an empty stomach disrupts normal metabolic processes and can spike stress hormones. It's always best to have it with or after a small, balanced meal.

An exclusive coffee diet would lead to high anxiety, nervousness, irritability, mood swings, chronic insomnia, and a powerful physical and psychological dependency on caffeine.

No. Any potential health benefits associated with coffee are found with moderate, balanced consumption (e.g., up to 4 cups a day) as part of a healthy diet, not as the sole source of sustenance.