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Fasting study: Impact of Buchinger Wilhelmi fasting on the composition of gut bacteria

Steffanie Hornstein - 29/11/2019 - 0 comments

The influence on the composition of gut microbiota of a ten-day fast following the Buchinger Wilhelmi programme: A study on fifteen healthy men

The composition of the intestinal flora plays an important role in preserving people’s health. This study examines the effect of a 10-day medically supervised periodic fast according to the Buchinger Wilhelmi method on the composition of the gut microbiota and on immunomodulatory parameters in 15 healthy men. It was determined that fasting in a healthy person reversibly alters the composition of the gut microbiota. While the effectiveness and safety of the Buchinger Wilhelmi programme was recently demonstrated in a study on 1,422 test subjects, the present study is an important foundation for other studies to examine the effects of fasting on the microbiome of sick people.


The study published in the Journal of Nutritional Sciences produced the following results:

  • The metabolic switch was accompanied by a change in the composition of the gut microbiota. Whereas the number of bacterial strains that play a role in the metabolization of carbohydrates and nutrition (e.g. Lachnospiraceae and Ruminococcaceae) decreased, there was an increase in bacterial strains that draw their energy from the metabolization of host-derived energy substrates (such as Bacteroidetes and Proteobacteria) with an inversion of the Bacteroidetes:Firmicutes ratio.
  • During refeeding, an increase in immunomodulatory proteins was observed (cytokines IL-6, IL-10, TNF-α, IFN-γ) in the blood as an indication of an immune reaction after reintroducing food.
  • Three months after fasting, the gut microbiota had the same composition as before fasting. Increased evidence of short chain fatty acids in the faeces can be seen as a positive effect of fasting as they help to protect the colon mucosa.
  • The typical metabolic switch that takes place during periodic fasting according to the Buchinger Wilhelmi method – from carbohydrates to fatty acid and ketone bodies as a main supplier of energy – resulted in an improvement of the metabolic parameters such as body weight, abdominal circumference, blood pressure and cholesterol. The subjects’ emotional and physical wellbeing also improved during fasting.

Mesnage, R., Grundler, F., Schwiertz, A., Le Maho, Y., & Wilhelmi de Toledo, F. (2019). Changes in human gut microbiota composition are linked to the energy metabolic switch during 10 d of Buchinger fasting. Journal of Nutritional Science, 8, E36. doi:10.1017/jns.2019.33
Wilhelmi de Toledo, F., Grundler, F., Bergouignan, A., Drinda, S., & Michalsen, A. (2019). Safety, health improvement and well-being during a 4 to 21-day fasting period in an observational study including 1422 subjects. PLoS One, 14(01).



Dr. Françoise Wilhelmi de Toledo

Dr. Robin Mesnage