A 36-year-old man experienced serious brain problems after fasting on water only for 40 days straight. He developed a rare condition called Wernicke’s encephalopathy, which happens when your body doesn’t get enough vitamin B1. This caused him to see double, lose his balance, and feel confused. Doctors treated him with high doses of vitamin B1 through an IV, and he got better. This case shows that extreme fasting can be dangerous even for healthy people, and doctors need to watch for this condition in people who fast, not just those who drink alcohol.

The Quick Take

  • What they studied: What happens to the brain when someone fasts on only water for an extremely long time (40 days)
  • Who participated: One 36-year-old man in good health who decided to do a 40-day water-only fast
  • Key finding: The man developed a serious brain condition from vitamin B1 deficiency that caused double vision, trouble walking, and confusion. Treatment with vitamin B1 helped him recover significantly.
  • What it means for you: Extreme water-only fasting can cause serious, life-threatening brain damage. If you’re considering extended fasting, talk to a doctor first. This is especially important because the damage can become permanent if not treated quickly.

The Research Details

This is a case report, which means doctors documented what happened to one specific patient. A 36-year-old man came to the hospital with serious symptoms after completing a 40-day water-only fast. The doctors examined him, took brain scans (MRI), and reviewed his medical history. They found that his brain showed specific damage patterns that matched a condition called Wernicke’s encephalopathy, which is caused by severe vitamin B1 deficiency.

The patient reported double vision, difficulty walking straight, and confusion. When doctors tested his nerves and brain function, they found problems with specific eye nerves and balance. The MRI scan showed swelling and damage in specific parts of his brain (the thalamus and area around the brain stem) that are known to be affected by vitamin B1 deficiency.

After diagnosis, the patient received high-dose vitamin B1 through an IV and had his electrolytes (important body salts) corrected. The doctors then tracked his recovery over time.

Case reports are important for identifying rare or unexpected problems that doctors might not normally think about. Most people know that vitamin B1 deficiency happens in people who drink too much alcohol, but this case shows it can happen in healthy people doing extreme fasting. This helps doctors recognize the warning signs in new situations.

This is a single case report, which is the lowest level of scientific evidence. It tells us what happened to one person, but we can’t say for certain that this will happen to everyone who fasts for 40 days. However, the diagnosis was confirmed with brain imaging, which makes it reliable. The case is valuable for alerting doctors to watch for this condition in fasting patients.

What the Results Show

The patient developed Wernicke’s encephalopathy after 40 days of water-only fasting. His main symptoms were double vision (diplopia), difficulty walking in a straight line (ataxia), and confusion. When doctors examined him, they found that specific nerves controlling eye movement weren’t working properly on both sides.

Brain imaging (MRI) showed damage in two specific areas: the medial thalamus (deep in the brain) and the area around the brain stem. These are the exact areas that get damaged when someone doesn’t have enough vitamin B1. This pattern of damage is a classic sign of Wernicke’s encephalopathy.

After receiving high-dose vitamin B1 through an IV and correction of electrolyte imbalances, the patient improved substantially. His symptoms began to resolve, showing that early treatment was crucial. The case demonstrates that this serious condition can develop in previously healthy individuals without any history of alcohol use.

The patient also had electrolyte imbalances (problems with important body salts like sodium and potassium), which are common after prolonged fasting. These imbalances were corrected as part of his treatment. The combination of vitamin B1 deficiency and electrolyte problems likely made his condition worse.

Wernicke’s encephalopathy is well-known in people with severe alcohol use disorder, where it affects about 1-2% of heavy drinkers. However, it can also occur in other situations involving malnutrition, including eating disorders, extreme dieting, and prolonged fasting. This case adds to a small but growing body of evidence showing that extreme fasting is a risk factor. Most previous cases involved people with underlying health conditions or eating disorders, making this case notable because the patient was otherwise healthy.

This is a single case report, so we cannot determine how common this problem is or predict who is most at risk. We don’t know if the patient had any underlying conditions that made him more vulnerable. The report doesn’t tell us about other people who may have fasted for 40 days without developing this condition. We also don’t have long-term follow-up information about whether the patient had any lasting effects. Case reports are useful for raising awareness but cannot prove that fasting always causes this problem.

The Bottom Line

Do not attempt extended water-only fasting without medical supervision. If you’re interested in fasting for health reasons, consult with a doctor first. If you do fast, ensure you’re getting adequate nutrition and vitamin supplementation. If you experience double vision, confusion, difficulty walking, or other neurological symptoms during or after fasting, seek emergency medical care immediately. (Confidence: High - based on clear medical evidence of serious risk)

Anyone considering extended fasting should read this. People with eating disorders, those on restrictive diets, and individuals interested in extreme fasting practices need to understand the risks. Healthcare providers should be aware that Wernicke’s encephalopathy can occur in non-alcoholic patients. This is less relevant for people doing short-term fasting (under 24 hours) with medical supervision.

Symptoms of vitamin B1 deficiency can develop within days to weeks of inadequate intake. Once symptoms appear, they can worsen rapidly. With treatment, some improvement may be seen within hours to days, but full recovery can take weeks to months. Permanent brain damage can occur if treatment is delayed.

Want to Apply This Research?

  • If using an app to track fasting, set alerts to stop any fast lasting longer than 24 hours without medical approval. Track any neurological symptoms (vision changes, balance problems, confusion) and alert users to seek medical care immediately if these occur.
  • Instead of attempting extended water-only fasts, use the app to track supervised intermittent fasting (like 16:8 or 5:2 diets) that includes nutrient-dense foods. Include vitamin B1-rich foods in your eating windows, such as whole grains, pork, legumes, and nuts.
  • If fasting, use the app to monitor daily nutrition intake and ensure adequate vitamins and minerals. Set reminders for symptom checking (vision, balance, mental clarity). Log any unusual neurological symptoms and create automatic alerts to contact a healthcare provider if concerning symptoms develop.

This case report describes a serious medical condition that developed after extreme fasting. It is not medical advice and should not be used to diagnose or treat any condition. If you are considering fasting of any duration, consult with a qualified healthcare provider first. If you experience symptoms such as double vision, confusion, difficulty walking, or other neurological changes, seek emergency medical care immediately. This information is for educational purposes only. Individual health outcomes vary, and this single case does not represent what will happen to all people who fast.