The World Record: What Is the Longest Fasting Period?

October 13, 2025 •

3 min read

In 1965, a Scottish man weighing 456 pounds began a medically supervised fast that would ultimately last 382 days. This remarkable story documents what is the longest fasting period on record, showcasing an extreme feat of human endurance under strict medical observation. However, modern medical professionals strongly advise against attempting such a prolonged fast due to significant health risks.

Quick Summary

The longest medically supervised fast was undertaken by Angus Barbieri, who went 382 days without solid food and lost 276 pounds. The fast, which took place in 1965-1966, was monitored by doctors and included vitamin and electrolyte supplements. While successful for Barbieri, such an extreme regimen is considered exceptionally dangerous for the general population.

Key Points

Longest Recorded Fast: The longest medically supervised fast was 382 days, completed by Angus Barbieri in Scotland in 1965-1966.
Constant Medical Supervision: Barbieri's fast was successful only due to strict medical observation, regular blood tests, and supplementation with vitamins and electrolytes.
High-Risk Endeavor: Prolonged fasting is extremely dangerous and poses severe risks, including electrolyte imbalance, organ damage, and heart failure.
Guinness Discourages Record: The Guinness Book of World Records no longer certifies fasting records to prevent and discourage unsafe dieting behaviors.
Refeeding Syndrome Risk: Reintroducing food too quickly after a prolonged fast can cause refeeding syndrome, a potentially fatal complication.
Modern Fasting Methods: Today, safer and medically supported alternatives like intermittent fasting are recommended, with careful attention to individual health conditions.
Consult a Doctor: Any fasting regimen beyond 24 hours should only be done under the supervision of a healthcare professional.

The World Record for the Longest Medically Supervised Fast

The undisputed record for the longest medically supervised fast belongs to Angus Barbieri, a 27-year-old man from Tayport, Scotland. In 1965, Barbieri, who weighed 456 pounds, began a period of therapeutic starvation at Maryfield Hospital in Dundee. His fast lasted an astonishing 382 days, concluding in July 1966 when his weight had dropped to 180 pounds. Throughout this time, he consumed only non-caloric liquids and supplements. This event, later recorded in the Guinness Book of World Records, remains a unique and historical medical anomaly.

Angus Barbieri's Remarkable Journey

Barbieri's fast was a meticulous, supervised effort. During the fast, he consumed only tea, coffee, sparkling water, and vitamin and electrolyte supplements. His doctors at the University of Dundee regularly monitored his health, taking blood and urine samples to track his progress and ensure his safety. Despite consistently low blood glucose levels during the latter eight months, he remained largely without adverse effects, a fact that amazed his medical team. This was a crucial factor in the fast's success; without continuous monitoring and supplementation, the risks would have been catastrophic.

The Health Risks of Prolonged Fasting

While Barbieri's case is a testament to human resilience, it is essential to understand that his outcome is not typical and cannot be safely replicated. Prolonged fasting carries severe health risks, including nutrient and electrolyte imbalances, cardiac stress, and organ failure. The body's shift from burning glucose to burning fat and, eventually, muscle tissue can have devastating consequences without careful medical supervision. Today, organizations like Guinness World Records no longer certify fasting records to avoid encouraging dangerous behavior.

Medically Supervised vs. DIY Fasting


Aspect	Medically Supervised Prolonged Fast	DIY Prolonged Fasting
Safety	High supervision, monitoring of vitals, blood work, and electrolyte levels.	Extremely dangerous; no supervision, high risk of severe complications and death.
Duration	Planned and managed for a specific therapeutic purpose (e.g., extreme obesity).	Unregulated and often impulsive, increasing the risk of over-extension and harm.
Nutrient Intake	Controlled intake of vitamins, minerals, and electrolytes to prevent deficiencies.	Non-existent or insufficient nutrient intake, leading to severe imbalances.
Body's Response	Adaptive physiological changes are managed and tracked to ensure safety.	Unmonitored, leading to unpredictable and potentially fatal metabolic shifts.
Outcome	Goal-oriented with documented, monitored results and follow-up care.	High risk of serious health issues, potential refeeding syndrome, and rebound weight gain.

Modern Approaches to Fasting

Modern medical science recognizes the benefits of controlled fasting, particularly intermittent fasting (IF) and time-restricted eating (TRE). These methods involve shorter fasting periods, ranging from 12 to 48 hours, and are not akin to the therapeutic starvation Barbieri underwent. Research on these shorter fasts points to potential benefits, such as weight loss, improved insulin sensitivity, and reduced inflammation, but even these practices should be approached with caution. Long-term fasting, even for a few days, can deplete essential nutrients and electrolytes, which is why a doctor's consultation is crucial for any fasting plan longer than 24 hours.

The Importance of Electrolytes and Refeeding

For any fast lasting over 24 hours, maintaining proper hydration and electrolyte balance is critical. Dehydration can occur quickly, and the depletion of minerals like sodium, potassium, and magnesium can lead to serious complications. Additionally, after a prolonged fast, the process of reintroducing food, known as refeeding, is extremely important. Refeeding syndrome, a potentially fatal complication, can result from a severe shift in fluid and electrolyte levels if food is reintroduced too rapidly. This is why Barbieri's refeeding process was carefully managed by his doctors over a period of ten days.

Conclusion: A Record to Admire, Not Emulate

Angus Barbieri's 382-day fast is a legendary story in medical history, illustrating the extreme limits of human endurance when under stringent, continuous medical supervision. However, it serves as a powerful cautionary tale rather than a blueprint for weight loss. The scientific community and health professionals unanimously advise against replicating such prolonged fasting due to the profound dangers involved. For those interested in the health benefits of fasting, safe, medically approved alternatives like intermittent fasting are available. Always consult a healthcare provider before undertaking any fasting regimen, especially a prolonged one. The remarkable outcome of Barbieri's fast was a singular, medically-monitored event that is exceptionally risky and not recommended for anyone today.

Frequently Asked Questions

Angus Barbieri holds the record for the longest medically supervised fast, lasting 382 days from June 1965 to July 1966. He lost 276 pounds during this time while consuming only non-caloric liquids and supplements.

No, prolonged fasting is generally not safe and carries significant health risks, including heart strain, nutrient deficiencies, and organ failure. The record-setting fast was performed under strict medical supervision and is not advised for the general public.

Therapeutic fasting, like Barbieri's, involves extended periods without solid food and requires constant medical monitoring. Intermittent fasting (IF) involves cycling between shorter periods of eating and fasting, typically 12-48 hours, and is less extreme.

During a prolonged fast, the body first uses up stored glucose. After about 24 hours, it begins converting fat into energy in a process called gluconeogenesis. Without proper electrolyte supplementation, this process can lead to metabolic imbalances and organ stress.

Refeeding syndrome is a dangerous metabolic disturbance that can occur if food is reintroduced too quickly after a long period of starvation. It can lead to severe fluid and electrolyte shifts, causing potentially fatal cardiac and neurological complications.

Guinness World Records stopped recording fasting feats to discourage individuals from attempting such dangerous and potentially life-threatening activities. The move was made due to concerns over public safety and potential harm.

While the exact time can vary, most people cannot survive more than about five days without water. With access to water, a healthy person can potentially survive for a month or two without food, but the process is extremely dangerous and unhealthy.