Results from the world’s largest study on fasting

Dr. Françoise Wilhelmi de Toledo

In Brief

  • The Facts:
    • The world’s largest study on fasting was published in 2019 by doctors and scientists from Buchinger Wilhelmi, the world’s leading clinic on therapeutic fasting.

    • The study documented numerous health benefits as a result of fasting.

    • Study participants fasted 4-21 days.

  • Reflect On:
    • With so many documented benefits of fasting, why is it not more mainstream?

    • Many sick people could be helped fairly simply and easily, is it because fasting can be done for free?

Fasting has been shown to have tremendous health benefits and can be used to treat and cure a wide variety of diseases and ailments. These benefits have been documented by researchers for decades, yet fasting as a health intervention is rarely “prescribed” by doctors. This is perhaps because unlike a pill, fasting isn’t profitable for big pharmaceutical companies. People can do it for free.

The German clinic Buchinger Wilhelmi is considered to be (one of) the world’s leading clinics for therapeutic fasting. It was initiated by Dr. Otto Buchinger, one of the first doctors to document the beneficial effects of fasting for a number of diseases in 1920Descendants of his family and four generations of doctors have continued to hone the method and document it scientifically.

The largest scientific study on the effects of Buchinger therapeutic fasting carried out to date was published in 2019. It was conducted by the clinic, led by Dr. Françoise Wilhelmi de Toledo (in the video below) in cooperation with Prof. Andreas Michalsen from Charité University Hospital in Berlin.

The study collected and evaluated data from 1,422 subjects (41 % male, 59 % female), who completed the Buchinger Wilhelmi fasting program over a period of 5, 10, 15 or 20 days in 2016. Under the title “Safety, health improvement and well-being during a 4 to 21-day fasting period in an observational study including 1422 subjects”, the study shows that Buchinger therapeutic fasting is safe and therapeutically effective. It also promotes emotional and physical well-being.

Below is an informative video interview with Dr. Toledo, lead author of the study and the head of research at Buchinger Wilhelmi summarizing the benefits of fasting and what the study discovered.



The study provided detailed evidence that:

  • Fasting mobilizes the energy stored in the fatty tissue of the human body. The metabolism switches from glucose to fat and ketone consumption, causing many beneficial effects. The metabolic change was documented in the study by the permanent presence of ketone bodies in the urine.
  • Fasting leads to significant weight loss, a reduced abdominal circumference, and lower cholesterol and blood lipid levels.
  • Fasting also normalized blood pressure and improved diabetes parameters such as blood sugar and HbA1c, thus improving many factors that contribute to a healthy cardiovascular system.
  • Furthermore, in 84 % of cases, serious health conditions such as arthritis, type 2 diabetes as well as fatty liver and hypercholesterolemia, high blood pressure and fatigue improved through fasting.
  • 93 % of the subjects did not feel hungry during fasting, which contributed to their emotional and physical well-being.
  • Medically supervised fasting had only very few side-effects, which could be treated easily and without interruptions to fasting. In individual cases, subjects experienced restless sleep, headaches, tiredness or lumbar spine complaints during the first three days.

In summary, this particular fasting program has been shown to be a safe and well-tolerated approach to prevent age-related illnesses and treat chronic metabolic disorders, including weight issues.