The 382-Day Angus Barbieri Fast: The Definitive Longest Fasting Study
The most famous and frequently cited answer to the question "What is the longest fasting study?" is the case of Angus Barbieri, a morbidly obese 27-year-old Scottish man. Under strict medical supervision at Maryfield Hospital in Dundee, Barbieri undertook a fast lasting 382 days, from June 1965 to July 1966. His doctors initially planned a much shorter fast, but Barbieri insisted on continuing as he adapted remarkably well to the process. The study, documented in the Postgraduate Medical Journal, provides a rare and comprehensive look at the body's response to extreme, extended periods without solid food.
During his fast, Barbieri consumed only non-caloric fluids such as tea, coffee, and sparkling water. To support his physiological needs, he was given vitamins, electrolytes, and a small amount of yeast extract, which contains essential amino acids. He underwent regular hospital check-ups, and blood and urine samples were taken throughout the process to monitor his health. His remarkable journey resulted in a weight loss of 276 pounds (125 kg), shrinking his body mass from 456 pounds (207 kg) to a goal weight of 180 pounds (82 kg).
The Science Behind Barbieri's Survival
Barbieri's case demonstrated the body's incredible ability to adapt to severe food scarcity, a legacy from human evolutionary history. For a person with significant fat reserves, the body shifts from using glucose to burning stored fat for energy. This metabolic state, known as ketosis, allowed him to power his body and brain for over a year. Key observations from this groundbreaking study included:
- Metabolic Shift: After initial depletion of glucose stores, his body efficiently used fatty acids and ketone bodies for fuel.
- Stable Blood Glucose: Remarkably, his blood glucose levels remained consistently low but stable throughout the final eight months, without causing adverse symptoms.
- Sustained Energy: Despite consuming no solid food, he maintained enough energy for daily activities and even lived at home for much of the fast.
- Normal Function: A follow-up study in 1973 found that Barbieri had maintained a healthy weight and showed no ill effects from the prolonged fast.
Longest Repeated Fasting Observation
While Barbieri's case represents the longest single fast, a more recent study from 2024 documented the longest repeated fasting observation. This case report detailed a 92-year-old man who had undergone a 21-day medically supervised fast annually for 45 years. The study revealed that he maintained excellent physical and mental health, and an epigenetic analysis indicated his biological age was nearly six years younger than his chronological age. While not a continuous fast, this demonstrates the long-term effects of repeated therapeutic fasting and provides valuable longitudinal data.
Modern Research on Prolonged Fasting
Since the landmark Barbieri case, a vast body of research has explored the mechanisms and safety of fasting. Modern studies on prolonged fasting, typically lasting from 4 to 21 days under medical supervision, continue to uncover complex physiological adaptations. For instance, a 2025 study on a 9.8-day water-only fast found significant weight loss and enhanced lipid metabolism but also noted a temporary inflammatory response. Other findings include heightened cellular repair (autophagy), improved insulin sensitivity, and potential neuroprotective effects. However, these studies emphasize the transient nature of many molecular changes and highlight the need for more long-term research.
Comparison of Landmark Fasting Cases
| Feature | Angus Barbieri's Fast | 92-Year-Old Repeated Fasting Case | Modern Prolonged Fasting Studies |
|---|---|---|---|
| Duration | 382 consecutive days (longest single fast) | 21 days annually for 45 years (longest repeated fast) | Typically 4 to 21 consecutive days |
| Supervision | Very close medical supervision at a hospital and as an outpatient | Yearly medical supervision at a specialized clinic | Medical supervision often required, especially for longer durations |
| Dietary Intake | Non-caloric fluids, vitamins, electrolytes, and yeast | Non-caloric fluids and a subsequent calorie-restricted diet | Varies by study; often water-only or modified calorie-restricted |
| Primary Outcome | Massive weight loss for obesity treatment | Healthy aging and epigenetic benefits | Metabolic health, insulin sensitivity, cellular repair |
| Ethical Context | Conducted in the 1960s before current stringent ethical guidelines | Conducted with long-term, repeated consent from a willing participant | Follows modern, strict ethical and safety protocols |
The Critical Role of Medical Supervision
Angus Barbieri’s case, while remarkable, serves as a cautionary tale as much as a scientific curiosity. Ethical guidelines for medical research have evolved considerably, and such an extreme fast would not be conducted today without very strict parameters. The success of Barbieri's fast depended heavily on his constant medical monitoring and supplementation, which prevented dangerous electrolyte imbalances and other complications. In fact, numerous sources, including the Guinness Book of Records, have long discouraged replicating such a fast due to the significant health risks involved. Medical experts universally stress that prolonged fasting should only be attempted under the careful eye of a healthcare professional.
The Ethical Constraints of Long-Term Fasting Studies
The fundamental challenge in answering "what is the longest fasting study?" is that the ethical implications prevent modern, controlled trials from replicating such extreme conditions. Research involving long-term starvation poses significant risks to human health, including heart failure and electrolyte disturbances. For this reason, modern research has focused on safer, shorter, and repeatable protocols like intermittent fasting and time-restricted eating, or on observing cases like the 92-year-old participant at specialized clinics. The findings from these modern, ethically sound studies, while less dramatic, provide more generalized and actionable health insights for the broader population.
Conclusion: Contextualizing the Longest Fasting Study
The question of the longest fasting study points directly to the extraordinary 382-day case of Angus Barbieri, a feat that remains a medical benchmark. While it provides unparalleled data on human endurance, it also underscores the critical importance of medical supervision in prolonged fasts. Subsequent and more modern research, such as the decades-long repeated fasting observation at Buchinger Wilhelmi, offers more practical and repeatable insights into the long-term health effects of fasting. The ethical constraints of modern science mean that Barbieri's record is unlikely to be broken in a clinical setting. Instead, researchers continue to focus on safer, shorter fasting windows to unlock potential health benefits for a wider audience, balancing scientific curiosity with patient safety.
Features of a successful therapeutic fast of 382 days' duration
