Buchinger Fasting
The European Clinical Fasting Tradition
Evidence grade 2 of 5, Thin. Read how the Atlas grades evidence.
2 human trials, about 40 studies, Large clinic case series (tens of thousands). The written rationale for this grade is still being prepared.
- FDA
- Practiced as supervised clinical care, mainly in Germany
- WADA
- Not prohibited
Reference only. Not medical advice.
What can go wrong
Buchinger fasting is conducted under medical supervision precisely because prolonged fasting carries real risks, including electrolyte disturbance, refeeding syndrome, and interactions with medications such as those for blood pressure and diabetes. The clinic model is designed to monitor and mitigate these; the same fast attempted unsupervised at home is considerably riskier, and the clinic safety record does not transfer to that setting. It is not appropriate for people who are underweight, pregnant or breastfeeding, or who have certain medical conditions. Because prolonged or restrictive fasting can be harmful for anyone with a history of disordered eating, and these are sensitive areas, decisions about fasting should be made with a qualified medical provider or registered dietitian, who can assess individual suitability. This entry is informational and is not medical advice or a protocol.
Buchinger fasting is a structured, medically supervised modified fast developed by German physician Otto Buchinger in the 1920s and still run at dedicated clinics in Germany and Spain. Unlike a pure water fast it permits small daily amounts of juice, vegetable broth, and honey (the clinics describe roughly 200 to 250 kcal per day), alongside movement, enemas, and supportive care. It is the most institutionalized therapeutic-fasting tradition in the West and the source of one of the largest real-world tolerability datasets for prolonged fasting. That flagship dataset is observational and clinic-funded, so it is best read as a safety and well-being signal rather than as proof that fasting treats disease. The supervised clinic setting is also exactly what the safety record reflects, and is not transferable to unsupervised fasting at home.
A century-old supervised European fasting method using small amounts of juice and broth, with the largest real-world safety record of any fast.
What people take it for
These are the reasons people give for taking it. They are not effects it has been shown to have.
What people get wrong
Often saidThe large 1,422-participant Buchinger study proves prolonged fasting is broadly safe and effective
ActuallyIt is an observational clinic cohort with no control group and no randomization, financed by Amplius GmbH and co-authored by clinic board members and a paid consultant. The paper itself flags 'restrictions regarding interpretation of efficacy' and notes its findings are specific to that clinic. It documents tolerability and self-reported well-being; it cannot establish disease-treatment efficacy or that unsupervised home fasting is equally safe.
Often saidBuchinger fasting has strong randomized-trial backing for treating disease
ActuallyThe randomized base specific to the Buchinger clinic method is small and preliminary. The exploratory NutriFast trial (n=53) of a 7-day Buchinger-style fast in rheumatoid arthritis found no statistically significant difference on its primary endpoint. A genuine older RCT (Kjeldsen-Kragh 1991, Lancet, n=53) supports fasting followed by a vegetarian diet in rheumatoid arthritis, but that is one small trial in one condition and a different intervention than the marketed clinic program.
Often saidBuchinger fasting is the same as a water fast
ActuallyIt deliberately includes small daily amounts of juice, vegetable broth, and honey, plus medical supervision and supportive care, which the clinics describe as making it gentler and more monitored than a pure water fast.
Who profits, and who pushes back
Andreas Michalsen
In his review of fasting therapy he and a co-author conclude that fasting 'should be further evaluated in controlled clinical trials and observational studies,' explicitly framing much of the current base as not yet confirmed by rigorous trials.
NutriFast trial investigators (Hartmann et al.)
Their own randomized trial reports that 'the between-group difference in the change from baseline to 12 weeks for the HAQ-DI was not statistically significant,' and they label the study exploratory rather than confirmatory.
Registered-dietitian and eating-disorder safety perspective
Supervised periodic fasting in a monitored clinic is one thing; the same protocols copied at home, or undertaken by people with eating-disorder vulnerability, are a real safety concern, and the clinic's reassuring numbers do not carry over to unsupervised use.
Buchinger Wilhelmi clinics
Sells this. Has a commercial interest in a product sold as this compound, as of July 2026.
Operate the flagship commercial clinics built on the method; they fund and publish much of the observational research, a genuine record but with an institutional interest.
Dr. Françoise Wilhelmi de Toledo
Sells this. Has a commercial interest in a product sold as this compound, as of July 2026.
Lead author on the large safety study; affiliated with the clinic network.
European integrative physicians
Incorporate supervised fasting within the German natural-medicine tradition, generally alongside conventional care.
Where the research comes from
Most of the published research on this comes from one place. 55% of it is from Germany. Findings that no unrelated group has reproduced are weaker than the study count makes them look.
| Place | Share of published research |
|---|---|
| Germany | 55% |
| Europe | 30% |
| Other | 15% |
Research published from: Germany, Switzerland, Global.
How we got here
Therapeutic fasting long predates the Buchinger name: deliberate abstention from food for healing and ritual appears across the ancient Mediterranean, in classical Greek medicine, in Islamic and Christian and South Asian ascetic traditions, and in many Indigenous practices. Otto Buchinger (1878 to 1966), a German naval physician discharged in 1917 with rheumatism, credited a 19-day fast in 1919 supervised by Dr. Gustav Riedlin in Freiburg with relieving his illness. In 1920 he opened his own fasting clinic in Witzenhausen and in 1935 published a book on the fasting cure that is still in print. His method became a pillar of German Naturheilkunde (natural medicine), and the family Buchinger Wilhelmi clinics carried it into the modern, more commercial era. In 2019 a large clinic-funded observational study gave prolonged fasting one of its most-cited real-world tolerability datasets, even as reviewers stressed its observational, clinic-funded nature.
- ancientTherapeutic and ritual fasting practiced across Mediterranean, Greek, Islamic, Christian, South Asian, and Indigenous traditions, long before any branded method
- 1919Otto Buchinger undergoes a 19-day supervised fast under Dr. Gustav Riedlin in Freiburg, which he credits with relieving his rheumatism
- 1920Buchinger opens his first fasting clinic in Witzenhausen, Germany
- 1935Buchinger publishes his book on the therapeutic fasting cure, still in print
- 1991Kjeldsen-Kragh et al. publish a single-blind randomized controlled trial in The Lancet on fasting followed by a one-year vegetarian diet in rheumatoid arthritis
- 2019Wilhelmi de Toledo et al. publish the 1,422-participant observational safety and well-being study in PLOS One; a 10-day Buchinger-fasting microbiome study also appears
- 2022NutriFast, an exploratory randomized controlled trial of a 7-day Buchinger-style fast in rheumatoid arthritis, reports a non-significant primary endpoint
At a glance
- Origin
- Otto Buchinger, 1920s Germany
- Intake
- ~200-250 kcal/day (juice, broth, honey)
- Setting
- Medically supervised clinics
- Largest dataset
- ~1,400-participant safety study
What this entry does not yet cover
What follows is unfinished work on our side, not a finding about Buchinger Fasting. A short entry is not a safe entry.
- Cost and market. We have not documented what it sells for or who sells it.
- Supply chain. We have not mapped where it is made.
- Who uses it. We have not documented the user groups.
- What could change. No forward-looking summary yet.
- How it compares. We have not set it against the alternatives.
- Children and teenagers. We have not checked what is known about younger people.
Sources
Flagship 2019 study is observational, n=1,422, clinic-funded, adverse events under 1 percent, well-being improved, with explicit efficacy-interpretation limitations
Wilhelmi de Toledo et al., PLOS One (full text via PubMed Central)
Same study, journal of record, peer-reviewed publication details and abstract
NutriFast exploratory RCT of a 7-day Buchinger-style fast in rheumatoid arthritis; primary endpoint not statistically significant (p=0.663)
Hartmann et al., Frontiers in Nutrition (full text via PubMed Central)
Classic randomized single-blind controlled trial of fasting followed by one-year vegetarian diet in rheumatoid arthritis
Review characterizes most fasting-therapy evidence as observational/empirical, with RCT confirmation only in rheumatoid arthritis, and calls for further controlled trials
Michalsen & Li, Forschende Komplementarmedizin / Research in Complementary Medicine (Karger)
Otto Buchinger biography: 1878 to 1966, naval physician, 1919 fast under Riedlin in Freiburg, 1920 first clinic in Witzenhausen, 1935 book
Clinic's own account of the method, its history, and the 200 to 250 kcal supervised protocol; institutional interest disclosed
Clinic frames the 2019 cohort as the world's largest fasting study; useful as the clinic's own positioning and disclosure of funding interest
Independent peer-reviewed study of 10-day Buchinger fasting and gut microbiota / metabolic switch in 15 healthy men
Mesnage et al., Journal of Nutritional Science (Cambridge Core)