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Changes in human gut microbiota composition are linked to the energy metabolic switch during 10 d of Buchinger fasting

  • Buchinger Wilhelmi
  • Institut für Mikroökologie

Abstract and Figures

Fasting is increasingly popular to manage metabolic and inflammatory diseases. Despite the role that the human gut microbiota plays in health and diseases, little is known about its composition and functional capacity during prolonged fasting when the external nutrient supply is reduced or suppressed. We analysed the effects of a 10-d periodic fasting on the faecal microbiota of fifteen healthy men. Participants fasted according to the peer-reviewed Buchinger fasting guidelines, which involve a daily energy intake of about 1046 kJ (250 kcal) and an enema every 2 d. Serum biochemistry confirmed the metabolic switch from carbohydrates to fatty acids and ketones. Emotional and physical well-being were enhanced. Faecal 16S rRNA gene amplicon sequencing showed that fasting caused a decrease in the abundance of bacteria known to degrade dietary polysaccharides such as Lachnospiraceae and Ruminococcaceae. There was a concomitant increase in Bacteroidetes and Proteobacteria ( Escherichia coli and Bilophila wadsworthia ), known to use host-derived energy substrates. Changes in taxa abundance were associated with serum glucose and faecal branched-chain amino acids (BCAA), suggesting that fasting-induced changes in the gut microbiota are associated with host energy metabolism. These effects were reversed after 3 months. SCFA levels were unchanged at the end of the fasting. We also monitored intestinal permeability and inflammatory status. IL-6, IL-10, interferon γ and TNFα levels increased when food was reintroduced, suggesting a reactivation of the postprandial immune response. We suggest that changes in the gut microbiota are part of the physiological adaptations to a 10-d periodic fasting, potentially influencing its beneficial health effects.
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Changes in human gut microbiota composition are linked to the energy
metabolic switch during 10 d of Buchinger fasting
Robin Mesnage
, Franziska Grundler
, Andreas Schwiertz
, Yvon Le Maho
Françoise Wilhelmi de Toledo
Gene Expression and Therapy Group, Kings College London, Faculty of Life Sciences & Medicine, Department of Medical and Molecular Genetics,
8th Floor, Tower Wing, Guys Hospital, Great Maze Pond, London SE1 9RT, UK
Buchinger Wilhelmi Clinic, Wilhelm-Beck-Straße 27, 88662 Überlingen, Germany
Charité-Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institut of Health,
Berlin, Germany
Institute of Microecology, Auf den Lüppen 8, 35745 Herborn, Germany
Université de Strasbourg, CNRS UMR 7178, Institut Pluridisciplinaire Hubert Curien, 23 rue du Loess, 67200 Strasbourg, France
Département de Biologie Polaire, Centre Scientique de Monaco, 8 Quai Antoine 1
, 98000 Monaco, Monaco
(Received 30 July 2019 Final revision received 2 October 2019 Accepted 8 October 2019)
Journal of Nutritional Science (2019), vol. 8, e36, page 1 of 14 doi:10.1017/jns.2019.33
Fasting is increasingly popular to manage metabolic and inammatory diseases. Despite the role that the human gut microbiota plays in health and diseases,
little is known about its composition and functional capacity during prolonged fasting when the external nutrient supply is reduced or suppressed. We
analysed the effects of a 10-d periodic fasting on the faecal microbiota of fteen healthy men. Participants fasted according to the peer-reviewed
Buchinger fasting guidelines, which involve a daily energy intake of about 1046 kJ (250 kcal) and an enema every 2 d. Serum biochemistry conrmed
the metabolic switch from carbohydrates to fatty acids and ketones. Emotional and physical well-being were enhanced. Faecal 16S rRNA gene amplicon
sequencing showed that fasting caused a decrease in the abundance of bacteria known to degrade dietary polysaccharides such as Lachnospiraceae and
Ruminococcaceae. There was a concomitant increase in Bacteroidetes and Proteobacteria (Escherichia coli and Bilophila wadsworthia), known to use host-
derived energy substrates. Changes in taxa abundance were associated with serum glucose and faecal branched-chain amino acids (BCAA), suggesting
that fasting-induced changes in the gut microbiota are associated with host energy metabolism. These effects were reversed after 3 months. SCFA levels
were unchanged at the end of the fasting. We also monitored intestinal permeability and inammatory status. IL-6, IL-10, interferon γand TNFαlevels
increased when food was reintroduced, suggesting a reactivation of the postprandial immune response. We suggest that changes in the gut microbiota are
part of the physiological adaptations to a 10-d periodic fasting, potentially inuencing its benecial health effects.
Key words: Periodic fasting: Buchinger fasting: Intestinal permeability: Inammation: Well-being
Alternation of food abundance and food scarcity (feast and
fast) is part of human and animal physiology. Fasting happens
on a daily basis, usually during night hours, but also during
short or longer periods of time, e.g. in humans without
access to technologies of food conservation
or for religious
. Humans also voluntarily fast because it has been
These authors contributed equally to this work.
Abbreviations: BCAA, branched-chain amino acid; BWC, Buchinger Wilhelmi Clinic; EDN, eosinophil-derived neurotoxin; LBP, lipopolysaccharide-binding protein; LPS,
lipopolysaccharide; sIgA, secretory IgA.
*Corresponding author: Françoise Wilhelmi de Toledo, fax +49 7551807806, email
© The Author(s) 2019. This is an Open Access article, distributed under the terms of the Creative Commons Attribution licence (http://creative-, which permits unrestricted re-use, distribution, and reproduction in any medium, provided the original work is
properly cited.
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documented to safely enhance well-being and to have thera-
peutic benets
. Most scientic investigations in the last
decade were, however, focused on intermittent fasting, a recur-
rence of 16 to 48 h energy restriction alternating with food
. By contrast, very few studies have examined
human physiology during a periodic fast lasting from 2 to
21 d or more, such as in the empirically based Buchinger
Wilhelmi fasting programme, described in peer-reviewed
therapeutic fasting guidelines
When animals or humans switch from eating to periodic
fasting, the source of energy for their cells switches from
food molecules absorbed through the gastrointestinal tract to
the utilisation of energy substrates mobilised out of several
body tissues, primarily adipose tissue but also body protein
In other words, there is a metabolic switch in energy utilisation
from glucose to fatty acids and ketones. This increase in the
rate of lipolysis and ketogenesis is reected by a decrease in
blood glucose, insulin, insulin-like growth factor-1, concomi-
tant to an increase in glucagon, growth hormone, NEFA,
ketone bodies and insulin-like growth factor binding protein-1
When the digestive tract is put temporarily at rest during peri-
odic fasting, it remodels its structure leading to a reversible atro-
phy as shown for rat intestinal villi
. In addition, changes in
gut motility, total intestinal mass
and microbiota compos-
ition have been described in the gut of fasting animals
The reduction of the external nutrient supply to the gut
microbiota, and the associated remodelling of the gastrointes-
tinal tissues of the host, have been qualied as a microscopic
energy crisiscoupled to a housing crisisfor the gut
. The gut microbiota relies almost entirely on
host diet composition as well as on host food processing
capacity to obtain metabolic substrates, and to cover its energy
requirements of 150450 kcal/d (6281883 kJ/d)
. It seems
therefore inevitable that periods of fasting where no external
food enters the digestive tract have repercussions on the
microbiota composition.
Changes in gut microbiota caused by fasting have been stud-
ied in hibernating animals like hamsters
, squirrels
brown bears
. Another study described shared responses
of the microbiota across ve vertebrates of different classes
(tilapia, toads, geckos, quail and mice) during prolonged fast-
. The most common response was a decrease in the
abundance of microbial species using plant glycans as a source
of energy, while species using host glycans as a source of
energy had their abundance increased
. Despite the growing
interest in several patterns of fasting and particularly periodic
fasting, its effects on the human microbial ecosystems remain
essentially unknown
Since dietary changes have a large impact on the gut micro-
biota, it is likely that fasting can also trigger important gut
microbiota changes, which may in turn inuence host health
and immunity
. This has been demonstrated in laboratory
animals, already. In mice, intermittent fasting prevents diabetic
retinopathy by restructuring the gut microbiota
. Other pub-
lications link therapeutic effects of fasting to changes of gut
microbiota in patients with rheumatoid arthritis
. Only
one study performed in human subjects showed that after 1
week of fasting, followed by 6 weeks of refeeding and probiotic
supplementation, an increase in abundance of lactobacilli,
Enterobacteriaceae and Akkermansia could be observed within
the gut microbiota
. However, the gut microbiota compos-
ition was not measured at the end of the fasting period.
To our knowledge no study so far has been performed to
investigate the effects of periodic fasting on the gut microbiota
in humans using high-throughput sequencing
. In order to
ll this important gap, we studied the composition of the
gut microbiota and a large range of health biomarkers in a
cohort of fteen healthy men before, on the last day of fasting,
during the refeeding-period and 3 months after a 10-d periodic
Buchinger fasting.
Materials and methods
Study design
This study was conducted according to the guidelines laid
down in the Declaration of Helsinki and all procedures involv-
ing human subjects were approved by the Baden-Württemberg
medical council (application no. F-2016-090; 27 September
2016). Written informed consent was obtained from all sub-
jects. The study was registered at the German Clinical Trials
Register (DRKS-ID: DRKS00011165, trial registry name:
Effects of the Buchinger Wilhelmi fasting programme on
energy metabolism and muscle function in humans (https:// 24 October
2016). It was conducted at the Buchinger Wilhelmi Clinic
(BWC) in Überlingen, Germany, between 20 November
2016 and 10 December 2016. All participants were in general
good health. Four time points were specied for each individ-
ual. The baseline examination was conducted 1 d before fast-
ing (time point 1). The second examination was done at the
end of the 10-d fasting period (time point 2). The third exam-
ination was conducted on the fourth day of the progressive
refeeding period after fasting (time point 3). The last examin-
ation took place 3 months after the fasting (time point 4). For
this follow-up, the subjects returned for 1 d to the BWC
between 1 March 2017 and 5 March 2017.
Participants were recruited in August 2016 among organisa-
tions involved in the practice of fasting, which is very popular
in Germany. Out of a total of fty-eight men, we recruited six-
teen men according to age, physical and psychological health
criteria. Included were men aged between 18 and 70 years
with a BMI between 20 and 32 kg/m
(26·5(SD 3·0) kg/
). One participant was excluded retrospectively due to
incomplete collection of stool samples. Thus, the data analysis
included fteen men (Fig. 1). The age of the participants was
SD 13·5) years. BMI was 26·5(SD 3·0) kg/m
. Exclusion
criteria were predened according to a list and included cach-
exia, anorexia nervosa, advanced kidney, liver or cerebrovascu-
lar insufciency
. Smoking and the intake of antibiotics
within the last 8 weeks, as well as the intake of probiotics
within the last 4 weeks, led to exclusion.
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Fasting intervention
All subjects fasted according to the fasting programme of the
BWC which is documented in the guidelines of the fasting
. They stayed under daily supervision of nurses and
physicians specialised in fasting therapy. On the day of admis-
sion in the BWC the participants received a standardised low-
carbohydrate vegetarian dinner. On the next day before the
beginning of the fast, the participants were given a 600 kcal
(2510 kJ) vegetarian diet consisting of rice and vegetables
divided in three meals. During fasting all subjects were
asked to drink 23 litres of water or non-energy herbal teas
on a daily basis. Additionally, all participants received a portion
of 20 g honey. Furthermore, an organic freshly squeezed fruit
juice (250 ml) was served at noon and a vegetable soup (250
ml) in the evening. On average, the total daily nutrient com-
position is described in Table 1. With the beginning of fasting
the subjects entered a standardised programme of physical
exercise alternating with rest. The exercise programme con-
sisted of outdoor walks and gymnastic groups. The whole pro-
gramme was supervised by certied trainers. To initiate the
10-d fasting period, the intestinal tract was emptied through
the intake of a laxative (2040 g NaSO
in 500 ml water
according to body weight). During the fasting period an
enema (1 litre water at 37°C) was applied by a certied
nurse every second day. This procedure, whose effects remains
to be investigated in a clinical study, is assumed to remove
intestinal remnants of the last meals, desquamated mucosal
cells from the gastrointestinal walls and basal secretions both
occurring during fasting. Based on clinical and empirical
observations, it facilitates the transition to the fasting mode,
leads quicker to the fasting-specic absence of hunger, and
prevents common symptoms observed at the beginning of
the fasting like headaches and fatigue. Although the safety of
enemas is still debated, their use for more than 60 years at
the BWC has never been linked to clinical complications.
From the tenth day of fasting on, food was stepwise reintro-
duced during the following 4 d. The food consisted of an
ovo-lacto-vegetarian organic diet with a progressive increase
of energy from 3347 to 6694 kJ/d (800 to 1600 kcal/d)
(Supplementary Table S3). The third faecal sample was
obtained from the rst defecation after refeeding, varying
between the rst and fourth refeeding day.
Clinical parameters
All participants underwent a thorough physical examination,
their medical history was documented and their height was
assessed in the admission consultation by the physician (Seca
285; Seca). Every morning trained nurses recorded body
weight while the subjects wore only underclothing (Seca 704;
Seca). Blood pressure and heart frequency were measured at
the non-dominant arm in a sitting position (upper-arm
blood pressure monitor, boso Carat professional; BOSCH +
SOHN GmbH u. Co. KG). Waist circumference was deter-
mined with a measuring tape mid-way between the lowest
rib and the iliac crest (openmindz® GmbH). The participants
self-reported their physical and emotional well-being on
numeric rating scales from 0 (very bad) to 10 (excellent).
Also, 3-d food protocols were documented prospectively by
each subject before fasting and 3 months afterwards. The
safety of the Buchinger Wilhelmi periodic fasting programme
was continuously monitored by a staff of doctors and nurses.
Biochemical parameters
Blood samples were collected by trained physicians in the
morning and drawn into EDTA (S-Monovette
2·7ml K3
Fig. 1. Flow chart of the recruitment procedure. BWC, Buchinger Wilhelmi Clinic.
Table 1. Nutrient composition of the diet during fasting
Parameter Amount
Fat intake (g/d) 0·2
Protein intake (g/d) 1·8
Carbohydrate intake (g/d) 56·2
Fibre intake (g/d) 1·1
Energy intake 234·4
kJ/d 980·7
kcal/d 234·4
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EDTA), citrate (S-Monovette
3 ml 9NC, citrate 3·2%
(1:10)), and blood sedimentation tubes (S-Sedivette
4NC, ESR/citrate buffer (1:5)), and were gently shaken after
lling. Additionally, serum tubes including serum gel with clot-
ting activator (S-Monovette
9 ml Z-Gel) were used and
stored upright for 30 min until coagulation with a subsequent
centrifugation step at 3920 gfor 10 min at room temperature.
All tubes were manufactured by Sarstedt AG & Co. The rou-
tine parameters were sent to MVZ Labor Ravensburg and ana-
lysed according to the manufacturers instructions in a fully
automated laboratory. Blood cell count (leucocytes, erythro-
cytes, Hb, mean cell volume, thrombocytes) was measured
using the blood analyser Sysmex XN-9000 (Sysmex Europe
GmbH). Glucose, total cholesterol and TAG were analysed
with ADVIA 2400 (Siemens Healthcare GmbH). Insulin
was measured with Centaur XP (Siemens Healthcare
GmbH). Remaining blood samples were immediately frozen
at 70°C.
Inammatory blood parameters were measured using the
Human High Sensitivity T Cell Panel kit (HSTCMAG-
28SK). Results were obtained by the Bio-Plex 200 Analyser
System and data were analysed with Bio-Plex Manager
software (Bio-Rad Laboratories). Bacterial lipopolysaccharide
(LPS) serum levels were measured by a commercial ELISA
kit (Cusabio). Antibodies specic for LPS were pre-coated
onto a microplate and 100 µl of standards or sample were
incubated for 2 h at room temperature. After incubation, sam-
ples were analysed at 450 nm. Values were expressed as pg/ml;
intra-assay and inter-assay CV were 8 and 10 %, respectively.
Plasma LPS-binding protein (LBP) was measured by a LBP
soluble ELISA kit (Hycult Biotechnology) according to the
manufacturers protocols.
The semi-quantitative concentration of ketone bodies was
self-measured in the rst morning urine using Ketostix
(Bayer AG) that react according to the concentration of acet-
oacetic acid.
Faecal parameters
Faecal samples were collected four times using sterile contain-
ers (MED AUXIL stool collector set; Süsse). The rst sample
was collected before the start of the fasting and the second fol-
lowing intake of a laxative (Laxoberal Abführ-Tropfen,
sodium picosulphate; Sano-Aventis Deutschland GmbH) in
the evening of the ninth fasting day. The third sample was
obtained from the rst defecation after refeeding and the
last sample in the follow-up phase. Faecal samples were imme-
diately frozen and stored at 70°C. The samples were sent to
the Institute of Microecology for analysis.
Faecal calprotectin and zonulin concentrations were mea-
sured by an ELISA as described elsewhere
. Faecal lactofer-
rin concentrations were determined using the IBD-SCAN
test (TechLabR, Inc.), faecal α1-antitrypsin concentrations
were analysed using the AAT test (Maier Analytic) following
the instructions. Lysozyme and β-defensin were measured by
an ELISA (Immunodiagnostik). Branched-chain amino acids
(BCAA), EDN (eosinophil-derived neurotoxin, eosinophil
protein x), sIgA and bile acid concentration were determined
with the BCAA, EDN, IDK
sIgA, and IDK
bile acids
test kits, respectively (Immunodiagnostik). SCFA were deter-
mined using GC as previously described
16S rRNA gene amplicon sequencing
In order to determine the composition of the gut microbiota
during the fasting intervention, we sequenced PCR-amplied
marker 16S ribosomal RNA genes fragments which contain
a bacterial taxa-specic region
. Microbial DNA was
extracted from 200 mg of faecal sample using the
DSP Virus/Pathogen Mini-Kit (Qiagen)
according to the manufacturers instructions on the
SP (Qiagen). DNA purity and concentration
were measured with an Implen NanoPhotometer P-Class 360
(Implen GmbH).
The partial sequences of the hypervariable region of the 16S
rRNA gene (V4 and V5) were PCR amplied using the primer
520 forward (5-AYTGGGYDTAAAGNG-3) and 907
amplication was performed at least twice for each sequencing
set up. The PCR mixture with a nal volume of 25 µl con-
sisted of 0·5 µl of each primer (10 µM), 0·6 µl of dNTP-mix
(10 mMeach), 5 µl KAPA HiPuffer including 20
(Roche), 0·1 µl KAPA HiPolymerase (Roche),
1 µl DNA isolate and lled up with nuclease-free water.
PCR reactions were performed in a T100 Thermal Cycler
(Bio-Rad Laboratories) using the following programme: 3
min at 95°C for initial denaturation, twenty-ve cycles of 30
s at 95°C for denaturation, 30 s at 55°C for annealing, and
45 s at 72°C for elongation, followed by a nal elongation
step for 5 min at 72°C. Water-template control and
Escherichia coli DNA as positive control were included for
each set of PCR reactions. Success of PCR were veried by
agarose gel electrophoresis using Midori Green as DNA-dye
(Biozym). Both PCR were pooled and puried with
Agencourt AMPure beads (Beckman Coulter) into 50 µl of
10 mM-Tris (tris(hydroxymethyl)aminomethane; pH 8·5).
A second PCR step was then performed to add unique
index barcodes with sequencing adaptors to the amplicon tar-
gets. The Ion Torrent set up custom-made index sequences
were chosen (added in the supplement; Integrated DNA
Technologies) as forward primer. The index PCR reaction
had a total volume of 50 µl and included 1 µl
Ion-index-primer forward and 1 µl 926Rcomb reverse primer
MTTTRAGTTT-3) for Ion-Torrent set ups with 1·l of
dNTP-Mix (10 mMeach), 10 µl KAPA HiPuffer includ-
ing 20 mM-MgCl
(Roche), 0·2 µl KAPA HiPolymerase
(Roche), 5 µl amplicon DNA and lled up with nuclease-free
water. PCR reactions were performed in a T100 Thermal
Cycler (Bio-Rad Laboratories) using the same programme as
above with eight cycles. Primers that were used were designed
for the V4 and V5 variable region of the bacterial 16S-rRNA
gene which led to a length of around 364 bp for bacterial iden-
tication. With indices and linker sequences, libraries have a
mean sequence length of 528 bp. After purication with
AMPure beads, quality checks for library sizes and DNA
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concentration were performed with the Aglient Bioanalyzer
using Aglient DNA 1000 chips (Agilent Technologies). To
determine the DNA concentration, the Qubit dsDNA HS
Assay Kit (Thermo Fisher Scientic) was used.
Libraries were nally pooled in equivalent 100 pMfor Ion
Torrent. Libraries prepared for Ion Torrent sequencing
template-positive Ion PGM template Hi-Q ion sphere particles
were produced using the emulsion PCR technique in the Ion
One Touch 2 and the Ion PGM Hi-Q OT2 Kit (Life
Technologies) following the manufacturers instructions for
PCR, recovery and quality control. The libraries were divided
to be run on four ION 318 chip-kit v2 BC chips (Life
Technologies) executing 850 sequencing ows on an Ion
PGM sequencer (Life Technologies) following the manufac-
turers instructions.
A total of six sequencing runs were performed. Each
sequencing run was processed separately in order to account
for the differences in sequencing quality. The 16S sequencing
data included a total of 31 556 258 reads (average of 498 493
reads per samples, range 70 8752 884 392) available as
demultiplexed FASTQ les on the SRA archive in the project
PRJNA531091. Data analysis was done with Rosalind, the
BRC/Kings College London high-performance computing
cluster. The DADA2 algorithm was used
to correct for
sequencing errors and identify amplicon sequence variants
(ASV) using R version 3.5.0. We trimmed the rst fteen
poor-quality bases at the 5side of reads as recommended
by the DADA2 manual
. A total of 20 728 sequence var-
iants was identied. The taxonomy was assigned using the
SiLVA ribosomal RNA gene database v132 up to the species
level. ASV with fewer than ten counts in less than 20 % of the
individuals were discarded. This resulted in a dataset com-
posed of 1673 ASV in sixty-three individuals that was brought
forward to a statistical analysis.
Statistical analysis
Justification of sample size. The sample size was calculated
based on the data obtained with Ramadan intermittent
fasting in a similar population
. Assuming a testretest
correlation coefcient for the measure of 0·9, a group of
fourteen subjects was necessary to detect a postpre
difference of about 7 % with a power of 0·95 and an αfor
unilateral test of 0·05.
The αdiversity, representing the diversity of the total num-
ber of species within the samples
, was measured using
Shannons diversity index, and the difference between groups
evaluated with the KruskalWallis rank sum test. We also mea-
sured the βdiversity, representing the diversity of the total
number of species between the samples
. We used the
BrayCurtis dissimilarity index which was calculated using
the R package Vegan and recommended for proportion data.
A stress function was used to measure the goodness of t
between the ordination and the original data. The 16S rRNA
gene amplicon sequencing dataset was further processed
using the R package Phyloseq in order to collapse the DNA
sequences to different taxonomic levels
. Relative abundance
values were transformed using the centred log-ratio (clr)
transformation with the R package compositions. We then per-
formed a statistical analysis of the differences in microbiota
composition between time points for each taxa and of the
associations between taxa abundance and health parameters,
by tting linear mixed models with lmer, considering repeated
sampling of individuals as random effects. Pvalues where cal-
culated using the difsmeans function with the R package lmert-
est. The Benjamini & Hochberg correction procedure was
applied to control the false discovery rate
The aim of this investigation was to describe the changes
within the gut microbiota caused by a 10-d fast. This was
done by measuring the microbiota composition and clinical
parameters 1 d before fasting (time point 1), at the end of
the 10-d fasting period (time point 2), on the fourth day of
the following progressive refeeding period (time point 3),
and 3 months after the fasting period (time point 4). Fasting
resulted in a signicant weight reduction of 5·9(
SD 0·8) kg
(P=0·0002). Abdominal circumference, systolic blood pres-
sure and diastolic blood pressure were also signicantly
reduced after fasting and at the end of the refeeding period
(Table 2). Furthermore, fasting was accompanied by an
enhancement of well-being (Table 2). Emotional well-being
increased at the end of fasting and was signicantly enhanced
after the refeeding period (P=0·00079). These parameters
returned to a baseline level 3 months after the fasting period.
Physical well-being also increased and reached signicant
enhancement after refeeding (P=0·000094), and was main-
tained 3 months after fasting (P=0·049).
Clinical data measurements
Clinical data measurements conrmed the energy metabolism
switch from carbohydrates to fatty acids and ketones (Fig. 2).
Glycaemic control improved during fasting: glucose and insulin
decreased signicantly at the end of fasting and the refeeding per-
iod (Fig. 2). Parameters of glucoregulation returned to baseline
levels 3 months after the fasting. TAG and total cholesterol
were signicantly reduced by the fasting period (Fig. 2).
Acetoacetic acid in urine increased signicantly during fasting
) and declined during refeeding (P=3·8×10
Microbiome analysis
We identied 213 unique species in the gut microbiota of f-
teen individuals. The results from the 16S rRNA gene ampli-
con sequencing were validated by a taxa-specic quantitative
PCR: the Spearmans rank correlations between these two
methods for eight taxa were all statistically signicant (P
) (Supplementary Fig. S1). The compos-
ition of the microbiota was highly individualised (Fig. 3(A)).
There were no differences in α-diversity (Fig. 3(B)).
However, the comparison of BrayCurtis distances revealed
that the composition of the microbiota changed during the
course of the intervention (Fig. 3(C)). Even if fasting had
large effects on the gut microbiome composition, Bray
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Curtis distances of the samples for a given individual remained
lower than distances across individuals, showing that gut
microbiomes remained individualised even after fasting. We
then used linear mixed models to identify the bacterial species
which were the most affected (Fig. 3(D)). A total of thirty-one
sequence variants had their abundances signicantly changed
by the intervention (Supplementary Table S1). There was an
inversion of the Firmicutes:Bacteroidetes ratio (Fig. 3(D)).
Bacteroidetes (40·7 %) became the dominant taxa after
the fasting period due to a large decrease in the relative abun-
dance of Firmicutes (39·9 %). This included bacteria known to
degradedietary plant polysaccharides such as the Lachnospiraceae
family (Fusicatenibacter saccharivorans,Lachnospira pectinoschiza,
Coprococcus_2 eutactus,Pseudobutyrivibrio spp., Roseburia faecis)and
from the Ruminococcaceae family (Faecalibacterium prausnitzii,
Ruminococcus_1 bicirculans,Ruminococcus_2 bromii). There was a con-
comitant increase in Bacteroides abundance (Bacteroides nordii,
Bacteroides fragilis) and in Proteobacteria abundances (E. coli,
Bilophila wadsworthia). Following food reintroduction (days 10 to
14, from 3347 to 6694 kJ/d (800 to 1600 kcal/d)) the gut
microbiota composition reected a partial recovery (Fig. 3).
After 3 months, subjectsgut microbiotas had returned to a
basal level in comparison with the baseline established on the
day of arrival at the clinic.
Faecal metabolites
We measured the metabolism of the gut microbiota by measur-
ing the levels of SCFA and BCAA. The concentrations of the
main SCFA (acetate, propionate, butyrate) were not changed
by the fast. However, a statistically signicant decrease in
i-butyrate (P=0·005) and valerate (P=0·005) levels was
observed during the refeeding period. In contrast, the levels of
SCFA signicantly increased 3 months after the fasting in com-
parison with pre-intervention levels. This could be linked to the
increased abundance of the known SCFA producer Coprococcus
eutactus. BCAA increased signicantly (P=0·00005) during fast-
ing, returned to baseline after refeeding, and declined signi-
cantly (P=0·0003) after 3 months (Table 3).
Faecal biochemical markers
The levels in faecal markers of gut permeability (zonulin,
α1-antitrypsin, bile acids) were stable across the different
phases of the study (Table 3). Plasma LBP, which reects
the exposure to bacterial LPS, was signicantly decreased dur-
ing fasting and remained reduced during the refeeding period.
Faecal markers of intestinal inammation suggested an inam-
matory response after fasting that normalised after 3 months
(Table 3).
The levels of IL-6, IL-10, interferon γand TNFα, which
are markers of inammation, showed a trend towards increase
from the beginning to the end of fasting but this increase was
not signicant. Yet, 4 d after food was reintroduced, there was
a signicant increase in comparison with baseline levels of all
four cytokines (IL-6, IL-10, interferon γ, TNFα)(Table 3).
This suggest that an immune reaction associated with
inammation results mainly from food reintroduction.
Table 2. Summary of the changes in clinical biomarkers and well-being during fasting
(Mean values, ranges and standard deviations)
Parameter Pre-fasting End of fasting 3 d after After 3 months
Mean Range SD Mean Range SD PMean Range SD PMean Range SD P
Weight (kg) 85·770·5106·91·079·866·199·59·6 *** 79·766·5100·19·5 *** 81·970·499·58·3NS
BMI (kg/m
)26·520·432·33·024·719·230·02·7 *** 24·719·430·12·7 *** 25·521·131·82·6*
SBP (mmHg) 128·396158 14·6 121·1 104152 11·3 * 116·1 103140 9·6 *** 127·6 104142 10·2NS
DBP (mmHg) 81·65790 9·377·76487 6·5* 77·666100 9·0* 81·27295 7·2NS
Waist (cm) 92·776108 9·189·074106 9·0** 89·780104 7·5** 92·180108 7·1NS
Emotional well-being, score 010 7·3410 1·98·3210 2·1NS 9·1610 1·2 *** 7·9410 1·6NS
Physical well-being, score 010 6·8310 2·47·8110 2·4NS 9·0510 1·5 *** 8 510 1·4*
SBP, systolic blood pressure; DBP, diastolic blood pressure.
Significantly different at end of fasting in comparison with pre-fasting baseline levels: *P<0·05, **P<0·01, ***P<0·001 (ANOVA).
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Associations between microbiome composition and health
We ultimately evaluated if gut microbiota composition could be
associated with variations in markers of health. A total of fty
associations were statistically signicant (BenjaminiHochberg
adjusted P<0·05) out of the 4136 associations tested.
Although our relatively small sample size only allowed us to
draw limited conclusions, the bacterial species which were sig-
nicantly associated with biochemical parameters were also
the bacterial species mainly affected by fasting (Fig. 4). The
abundance in Lachnospiraceae (Coprococcus_2 eutactus,
Fusicatenibacter saccharivorans,andLachnospira pectinoschiza)was
positively associated with plasma glucose levels and negatively
associated with BCAA levels. By contrast, Bacteroidetes
(Bacteroides dorei/fragilis and Bacteroides thetaiotaomicron), as well as
aProteobacterium (Bilophila wadsworthia), presented the opposite
trend and were negatively associated with plasma glucose levels
and positively associated with BCAA levels.
There is a growing interest in biomedical research on fasting
and its therapeutic aspects
, as well as in the gut microbiota
and its inuence on human health
. Here we document
that periodic fasting in humans has major effects on
biochemical markers such as blood lipids, glucoregulation,
enhancement of emotional and physical well-being, and
the faecal microbiota. We observed a major decrease in the
relative abundance of the Firmicutes, Lachnospiraceae
and Ruminococcaceae, concomitant to an increase in
Bacteroidetes and Proteobacteria. This prole correlates well
with known effects of fasting in hibernating animals
and with daily cyclical uctuations in the composition of the
mouse gut microbiome according to feeding/fasting
. When mice are eating, usually during the night,
Firmicutes are proliferating and become the dominant phylum
while Bacteroidetes rise during fasting (daytime).
The changes in gut microbiome composition and energy
metabolism were reversed after 3 months. This reversibility
in healthy subjects does not rule out the potential of this fast-
ing protocol to change over the long term the gut microbiota
composition of ill subjects. A large number of studies have
indicated that unhealthy individuals tend to have a lack of
microbial diversity in their gut
. Since more diverse micro-
bial environments are known to be more resilient
hypothesise that the gut microbiome of unhealthy individuals
with a loss of diversity may have a different resilience to the
fasting intervention. Prolonged fasting is known to be an
Fig. 2. Metabolic switch from carbohydrates to fatty acids and ketones induced by a 10-d fasting. A regression spline was fitted on individual acetoacetic values to
show the variations in ketosis during the course of the study. The distribution is summarised by box plots, with the upper and lower hinges extending to the first and
third quartiles. Statistical significance was assessed with an ANOVA in comparison with pre-fasting baseline levels (* P<0·05, ** P<0·01, *** P<0·001). Biomarker
levels are presented for each individual across the four phases of the intervention (1, baseline examination; 2, at the end of the 10-d fasting period; 3, on the fourth
day of the following progressive refeeding (RF); 4, 3 months after the fasting period).
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Fig. 3. Fasting caused a decrease in the abundance of bacteria from the Lachnospiraceae and Ruminococcaceae families concomitant with an increase in
Bacteroidetes. (A) The gut microbiome of fifteen subjects undergoing a 10-d fasting was analysed by 16S rRNA gene amplicon sequencing. The taxonomic profiles
are presented for each individual (ID from 1 to 15) across the four phases of the intervention (1, baseline examination; 2, at the end of the 10-d fasting period; 3, on the
fourth day of the following progressive refeeding; 4, 3 months after the fasting period). (B) The αdiversity was not changed by fasting. (C) The measure of dissimi-
larities between samples (BrayCurtis distance) revealed that the samples separate by time point along the yaxis. (D) The evaluation of changes in species relative
abundances across the fasting period revealed that fasting caused a statistically significant decrease in the abundance of bacteria from the Lachnospiraceae family
(in green), and from the Ruminococcaceae family (in blue), concomitant with an increase in Bacteroidetes (in pink). The composition of the microbiome returned to a
basal level during refeeding. NMDS, non-metric multidimensional scaling. 8
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efcient therapy in humans to manage metabolic disorders like
obesity or high blood pressure
and rheumatoid arth-
. Yet, the present study was performed on healthy
subjects and further studies are therefore needed to determine
the effects of fasting, and their persistence, on the gut micro-
biome of patients with specic disorders. Furthermore, fasting
can be considered as a metabolic training switching from glu-
cose to fat and ketose and back
. Healthy subjects gain con-
dence that fasting is safe and may be used in the case of
weight gain, metabolic disorders and other diseases which
can be improved by periodic fasting as well as intermittent
fasting. When used with a therapeutic goal a special focus is
made on the maintenance phase fasting to consolidate the
results. Our study lays the foundation for future studies to
investigate the impact of fasting on the microbiota of ill per-
sons and their relationship with metabolic and inammatory
Furthermore, it is the rst to explore the links between the
changes in gut microbiome caused by periodic fasting and the
changes in inammation and gut permeability. During periodic
Buchinger fasting, almost no nutrients are ingested and conse-
quently absorbed by the small intestine. Therefore, a signi-
cant postprandial increase in gut permeability does not
occur. This is reected by the lack of changes in gut perme-
ability markers in our study population in accordance with
earlier data
. However, effects of a periodic fasting on gut
permeability may differ between healthy subjects and patients
with metabolic disorders. In a previous study, a 4-week energy
restriction (800 kcal/d (3347 kJ/d)) in twenty obese women
reduced gut permeability
. Additionally, the gut barrier pro-
tects the host from inux of bacterial components such as
LPS, components of the outer membrane of Gram-negative
bacteria. A biomarker for the translocation of LPS is the
. In our cohort LBP decreased signicantly during fast-
ing, probably reecting the decreased food intake.
Interestingly, although we observed no changes of further
inammation markers during the fasting period, all inamma-
tion markers, except for LPS increases signicantly after food
reintroduction. This suggests that food intake reactivated the
postprandial immune response.
In our cohort, we observed a decrease in blood leucocyte
count. This was associated with an initial autophagy triggered
by fasting, followed by the activation of bone marrow stem
. The modulation of the immune response by fasting
is also shown by the increase in faecal lysozyme during fasting
and refeeding, indicating migration of leucocytes into the gut.
This is corroborated by the increase in secretory IgA (sIgA),
known for their protective action on the mucosal surface
An increase in sIgA levels was also demonstrated in a previous
study after 17-d Buchinger fasting, and correlated with
enhanced immune status
. Changes in bacterial antigens
are described in rheumatoid arthritis
concomitant to
improvement of the symptoms associated with fasting
The association between E. coli and sIgA levels detected in
our study suggests that the increase in sIgA levels during fast-
ing is due to the increased abundance in bacteria causing an
adaptive humoral local response. This is corroborated by
recent studies which have shown that commensal
Proteobacteria promote a T cell-dependent increase in serum
IgA in mice, conferring protection against sepsis
. In mice,
intermittent fasting increases resistance to Salmonella infec-
. Since sIgA are known to be the principal eosinophil
Time point
Time point
12 34
Time point
Time point
Ruminococcus_2 bromii (%)
Faecalibacterium prausnitzii (%)
Coprococcus_2 eutactus (%)
Lachnospira pectinoschiza (%)
Fusicatenibacter saccharivorans (%)Bacteroides fragilis SV_378 (%)
Roseburia faecis (%)
Bacteroides fragilis SV_96 (%)
Bacteroides nordii (%)
Ruminicoccus_1 bicirculans (%)
Time point
12 34
Time point
Time point
12 34
Time point
Time point
12 34
Time point
Fig. 3. Continued.
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mediator at mucosal surfaces, causing eosinophil degranula-
, we could hypothesise that the migration of leucocytes
into the gut can also explain the increase in EDN levels during
fasting. Altogether, general aspects of the communication
between micro-organisms of the digestive tract and the
immune system are well described
Although Proteobacteria are generally regarded to have a
negative inuence on physiological function
, with Bilophila
wadsworthia linked to the development of inammatory bowel
, it is important to note that effects are strain-
dependent. For instance, the probiotic E. coli Nissle 1917
strain can protect against the invasion by adherent-invasive
E. coli B2 strains
. It is thus not possible to denitely attri-
bute benecial or detrimental health effects to the increase
in Proteobacteria abundance observed in our study since the
method we used does not allow the determination of gut
microbiome composition at the strain level. We recommend
new investigations using shotgun metagenomics
Moreover, the absence of food intake and thus of digestive
processes and absorption during fasting should be taken into
consideration when evaluating possible health effects of a bac-
terial strain. The assessment of physical well-being and
gastrointestinal symptomatic outcomes in another study did
not indicate a pathological situation
The enhancement of well-being is one of the most contra-
intuitive effects of voluntary fasting, whereas involuntary
food deprivation is generally experienced as dreadful. The
mechanisms underlying this mood enhancement might be
similar to those by which physical exercise can induce bene-
cial responses in the brain, leading to improvements in the
processes of learning and memory formation
. A major con-
tributor is the modulation of brain-derived neurotrophic factor
(BDNF) levels by the ketone 3-hydroxybutyrate, as shown on
cultured cerebral cortical neurons via an effect on mitochon-
drial respiration
. Increasing levels of BDNF levels are also
linked to 5-hydroxytryptamine serum levels which are known
to increase during fasting, and which thus provide an explan-
ation for positive effects on mood
. It could also be hypothe-
sised that fasting-induced mood enhancement can be linked to
changes in the gut microbiota composition. This hypothesis is
corroborated by studies showing that the gut microbiota sup-
presses Bdnf expression in the hypothalamus in mice
Moreover, the administration of probiotics is a successful strat-
egy to reduce anxiety and indicates that changes in microbiome
Table 3. Serum and faecal biochemistry
(Mean values and standard deviations)
Pre-fasting End of fasting 3 d after After 3 months
Mean SD Mean SD PMean SD PMean SD P
Serum biochemistry
Erythrocytes (10
/μl) 5·22 0·55 5·16 0·40 NS 5·03 0·41 NS 5·23 0·48 NS
Hb (mmol/l) 9·48 0·76 9·36 0·45 NS 9·10 0·52 * 9·39 0·59 NS
Haematocrit (%) 44·90 3·27 43·64 2·33 NS 43·75 2·93 NS 44·79 3·00 NS
Leucocytes (10
/μl) 6·01 1·38 4·37 1·18 *** 3·98 0·93 *** 5·51·45 NS
MCV (fl) 86·34 4·19 84·75 3·35 NS 87·09 3·06 NS 85·89 4·25 NS
Thrombocytes (10
/μl) 234·93 42·28 247·53 41·85 NS 247·13 52·04 NS 258·43 42·36 *
Inflammation parameters in blood
IFNγ(pg/ml) 78·77 89·43 107·36 70·09 NS 173·95 43·82 *** 43·04 21·34 NS
IL-10 (pg/ml) 24·47 14·05 19·67 7·91 NS 34·85 12·06 *** 21·88 12·99 NS
IL-6 (pg/ml) 12·57 10·617·83 7·89 NS 28·42 7·01 *** 13·69 7·03 NS
TNFα(pg/ml) 71·68 79·26 111·03 71·82 NS 165·01 56·9 *** 40·41 21·93 NS
LBP (μg/l) 11·82 2·51 9·78 3·80 ** 9·58 2·62 ** 11·01 1·72 NS
LPS (pg/ml) 15·03 16·29 12·23 13·35 NS 8·93 11·11 NS 8·88 11·65 NS
Inflammation parameters in faeces
sIgA (ng/ml) 1860·35 1557·2 2812·33 2544·79 NS 3807·01 3013·58 ** 1642·06 1148·3NS
EDN (ng/ml) 404·69 305·63 1176·75 708·56 *** 676·6 701·13 NS 437·86 360·56 NS
β-Defensin (ng/ml) 39·17 47·39 61·23 50·28 NS 30·78 27·31 NS 56·46 89·87 NS
Lysozyme (ng/ml) 555·93 304·06 961·33 572·01 * 1183 658·06 ** 532·07 236·42 NS
Lactoferrin (μg/g) 1·71·74·312·1NS 4·812·6NS 1·81·8NS
Calprotectin (μg/g) 29·322·240·771·2NS 69·3 180·6NS 26·914·2NS
Bile acid (μmol/100 ml) 287·84 231·04 192·11 131·64 NS 212·13 117·87 NS 291·22 235·97 NS
Gut permeability parameters in faeces
Zonulin (ng/ml) 74·21 47·69 95·94 107·33 NS 94·13 114·01 NS 107·50 76·05 NS
α-1-Antitrypsin (mg/l) 394 232 520 343 NS 441 389 NS 401 218 NS
Microbial energy metabolism
Acetate (mM)63·848·354·333·6NS 65·958·3 NS 100·959·4*
Butyrate (mM)6·76·74·83·1NS 4·24·8NS 15·113·2**
i-Butyrate (mM)1·81·81·41·1NS 0·70·7** 1·71·1NS
Propionate (mM)9·57·48·54·7NS 9·610·7NS 17·312·8*
Valerate (mM)2·72·62·01·6NS 1·01·2** 2·61·9NS
i-Valerate (mM)1·10·81·00·5NS 0·60·8NS 1·81·2**
BCAA (μmol/l) 486·58 86·66 575·09 99·24 *** 455·51 67·79 NS 403·95 70·35 ***
MCV, mean corpuscular volume; IFNγ, interferon γ; LBP, lipopolysaccharide-binding protein; LPS, lipopolysaccharides; sIgA, secretory IgA, EDN, eosinophil-derived neurotoxin;
BCAA, branched-chain amino acids.
Significantly different at end of fasting in comparison with pre-fasting baseline levels: *P<0·05, **P<0·01, ***P<0·001 (ANOVA).
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proles have a direct impact on mood
. As far as well-being
during fasting is concerned, additional scientic investigations
are needed to understand the role of enemas in preventing
symptoms which are often observed at the beginning of the
fasting such as headaches and fatigue. Since enemas are
known to affect gut microbiome composition
important to separate the effects of the enema from the effects
of fasting in future studies. Furthermore, an interesting question
is whether the observed well-being-enhancing effect of fasting is
mainly due to the assumed ability of an enema to remove intes-
tinal remnants, desquamated mucosal cells and fasting basal
secretions from the gut or if it results from an effect of the
enema on gut microbiota composition.
The gut microbiota may also contribute to weight loss. In our
study, the taxonomic group which was most affected by the
reduction of nutrient supply was Lachnospiraceae, which is a
bacterial family known to have the highest energy-harvesting
. Studies demonstrated that a 20 % increase in
Firmicutes (i.e. Lachnospiraceae) was associated with an
increased energy harvest of about 150 kcal (628 kJ)
the intrinsic production of energy from the Firmicutes comes
in addition to the general energy intake, it can be hypothesised
that shutting down Lachnospiraceae-mediated increase of
energy uptake had an inuence on the weight decrease mea-
sured in this study. This is corroborated by the association
between Lachnospiraceae abundance and glucose levels. The
Fig. 4. Abundance of bacteria affected by fasting is associated with changes in health biomarkers. The abundance of bacterial species identified by 16S rRNA
sequencing was used as a predictor in linear mixed models to understand if they associate with health biomarkers. (A) Statistically significant associations were
found between markers of the energy metabolism switch and fasting-affected species. A total of five biochemical parameters are displayed along the bacteria asso-
ciated with their variations. All arrows indicate statistically significant associations (e.g. a decrease in glucose levels was associated with a decrease in
Lachnospiraceae abundance). (B) The abundance in Lachnospiraceae Coprococcus_2 eutactus (SV_299), Fusicatenibacter saccharivorans (SV_1010) and
Lachnospira pectinoschiza (SV_721) were consistently positively associated with plasma glucose levels, and negatively associated with branched-chain amino
acid (BCAA) levels. By opposition, the Bacteroidaceae Bacteroides dorei/fragilis (SV_96) and Bacteroides thetaiotaomicron (SV_600), as well as Bilophila wads-
worthia, presented the opposite trend and were negatively associated with plasma glucose levels, and positively associated with BCAA levels. EDN, eosinophil-
derived neurotoxin; sIgA, secretory IgA.
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micro-organisms inhabiting the human gastrointestinal tract
have the ability to ferment indigestible complex carbohydrates
and produce energy substrates such as SCFA which are then
taken up by the host. Up to 5 to 10 % of human energy require-
ments are covered by SCFA
. In general, SCFA concentra-
tions remained stable during fasting which is surprising since
they are mainly produced by fermentation of dietary bres
Furthermore, an increase in SCFA levels was noticed 3 months
after the intervention. Whether this is a consequence of the gut
microbiota structural changes due to fasting or a change in diet-
ary habits must be conrmed. Food protocols documented an
increase in bre intake 3 months after fasting (Supplementary
Table S2).
The association between Bacteroidetes abundance and
faecal BCAA levels in our study suggests that energy require-
ments in absence of dietary nutrients during fasting could be
sustained by the use of host-derived compounds such as des-
quamated cells. The species which have their levels increased
during fasting in our study are also those species known to
have the highest proteolytic activity in the gut microbiota
The clinical signicance of this switch in gut microbiome
metabolism is unclear. Experiments in mice showed that the
gut microbiome starts feeding on host mucins and degrade
the colonic mucus barrier when it is deprived of dietary
. Little is known about the fate of the mucus barrier
during fasting in humans. Starved broilers (also deprived of
water) have a thinner mucus adherent layer throughout the
small intestine
. However, this might not reect physiology
during prolonged fasting since the gut is known to undertake
substantial structural changes
. It should also be taken into
account that the microbial density is severely reduced during
fasting. During hibernation, microbial density decreases by
93·7 % in the caecum of hamsters
. This cannot be
evaluated in our study because the sequencing of 16S rRNA
gene amplicons is not quantitative, and because faecal micro-
biota is not fully reecting the intestinal microbiota.
In conclusion, 10 d of fasting led to a profound change
within the gut microbiota composition and function. The
reductions in body weight and waist circumference were asso-
ciated with an enhancement of well-being and an improvement
of energy metabolism. Refeeding induced an immune reaction,
as shown by circulating cytokines. This study on healthy sub-
jects lays the foundation for further investigations on the
impact of fasting on the microbiota and their relationship
with metabolic and inammatory mediators in diet-related
chronic diseases.
We thank the study patients for their participation and the
physicians and nursing staff of the BWC for their cooperation.
The present study was nanced by Amplius GmbH,
Überlingen, Germany. This company has the task to develop
a research department for the BWC Überlingen and
Marbella who are the funders. Amplius GmbH had no role
in the design, analysis or writing of this article. No additional
external funding was received for this study.
F. W. T., F. G. and Y. L. M. conceived and conceptualised
the study. A. S. provided expert input into the study design
and performed parts of the laboratory analyses (sequencing
and all faecal parameters). F. G. was project manager and
coordinated study conduction and data collection. R. M. coor-
dinated the writing of the paper and performed the bioinfor-
matics and statistical analysis. R. M., F. G. and F. W. T.
drafted the manuscript. All authors contributed to data inter-
pretation and the revision and editing of the nal manuscript.
F. W. T. is managing director of Amplius GmbH, in charge
of the scientic documentation for the BWC. Amplius GmbH
is a company that conceives, coordinates and develops fasting
research. All authors declare that no competing interests exist.
Supplementary material
The supplementary material for this article can be found at
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... Bacteroidetes and Proteobacteria, known to utilize host-derived energy substrates, simultaneously increased. Many previous studies have shown that dietary composition and behaviors are potent influences that can alter gut microbiota structure (David et al., 2014;Mesnage et al., 2019). Changes in dietary composition and behavior, such as prolonged fasting, can affect meal time and size, leading to rapid metabolic changes and altering the ratio of Firmicutes and Bacteroidetes (Jumpertz et al., 2011;Li et al., 2017Li et al., , 2020 Water-soluble fibers (g) Mean± SD 5.9 ± 1.8 4.7 ± 1.5 a 0.045 * Median (min-max) 5.7 (3.9-9.9) ...
... In our study, two bacteria were positively associated with fasting: Escherichia and Shigella. Mesnage et al. (2019) found that Escherichia coli were more abundant at the end of Ramadan fasting. Fasting-induced alterations in the gut microbiota may affect human energy metabolism since variations in taxonomic abundance were linked to changes in blood glucose and branchedchain amino acids in the feces (Mesnage et al., 2019). ...
... Mesnage et al. (2019) found that Escherichia coli were more abundant at the end of Ramadan fasting. Fasting-induced alterations in the gut microbiota may affect human energy metabolism since variations in taxonomic abundance were linked to changes in blood glucose and branchedchain amino acids in the feces (Mesnage et al., 2019). Maifeld et al. reported that following the refeeding period, a consistent decline in Enterobacteriaceae, one of its members, specifically Escherichia coli, was observed (Maifeld, 2021). ...
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Much research has been conducted regarding the impact of diet on the gut microbiota. However, the effects of dietary habits such as intermittent fasting are unclear. This study aimed to investigate the effect of intermittent fasting during Ramadan on the gut microbiota. The study was conducted on 12 healthy adult individuals who practiced fasting 17 h per day for 29 consecutive days during the month of Ramadan. To determine the dietary intake of individuals, a 3-day dietary record was kept at the beginning and end of the study. Reads that passed quality filtering were clustered, and custom-prepared 16S rRNA gene regions of bacteria associated with the human microbiome were used as a reference. Consensus sequences were created, and genus-level taxonomic annotations were determined using a sequence identity threshold of 95%. The correlations between the dietary intake measurements of the participants and the respective relative abundance of bacterial genera were investigated. The results showed that Firmicutes were higher in abundance in the gut microbiota before fasting among participants, while they were significantly lower in abundance at the end of Ramadan fasting ( p < 0.05). Proteobacteria were significantly higher in abundance at the end of the month of Ramadan ( p < 0.05). Fasting was associated with a significant decrease in levels of seven genera: Blautia, Coprococcus, Dorea, Faecalicatena, Fusicatenibacter, Lachnoclostridium , and Mediterraneibacter . Conversely, the abundances of two bacterial genera were enhanced at the end of the fasting month: Escherichia and Shigella . The results of the dietary intake analysis showed that a negative correlation was detected for three comparisons: Ihubacter and protein (rho = −0.54, p = 0.0068), Fusicatenibacter and vegetables (rho = −0.54, p = 0.0042), and Intestinibacter and nuts (rho = −0.54, p -value = 0.0065). The results suggest that even when the fasting period during Ramadan is consistent, the types of food consumed by individuals can affect the gut microbiota.
... In addition, the extent to which the composition of microbiota needs to be changed to influence host health is unclear. Several human studies have shown that DR has a fundamental and profound effect on gut microbiota, but this effect did not persist after the intervention ceased, suggesting that the gut microbiota were tended to remain stable and highly individual-specifc under DR (Mesnage et al. 2019;Ott et al. 2017;Sowah et al. 2022). Moreover, subjects were stratified into different enterotypes according to their baseline microbial composition after CR, and the effect of CR on the reduction in BMI was inconsistent. ...
... Accordingly, DR could modulate human gut microbiota, and the gut microbiota also has been proposed to affect some health benefits of DR. The most frequently found gut microbiota impact of DR in humans is the enrichment of Akkermansia (Dong et al. 2020;Ozkul, Yalinay, and Karakan 2020;von Schwartzenberg et al. 2021), Bifidobacterium (Dong et al. 2020;Mesnage et al. 2019;Ott et al. 2017), Faecalibacterium (Cignarella et al. 2018;Maifeld et al. 2021;Ozkul, Yalinay, and Karakan 2020;Ruiz et al. 2017;Zeb et al. 2020), and Parabacteroides (Ali et al. 2021;Benítez-Páez et al. 2021;Gutiérrez-Repiso et al. 2021;Stanislawski et al. 2021). Akkermansia and Bifidobacterium, the promising probiotics, have physiological advantages in several clinical settings. ...
... The Parabacteroides genus also has been associated with antimicrobial resistance and the beneficial effects in human health (Ezeji et al. 2021). However, the change of Bacteroides during DR is inconsistent (Ali et al. 2021;Benítez-Páez et al. 2021;Maifeld et al. 2021;Mesnage et al. 2019;Ruiz et al. 2017;Zou et al. 2020). Bacteroides is seen enriched during fasting and then depleted during refeeding. ...
In recent times, dietary restriction (DR) has received considerable attention for its promising effects on metabolism and longevity. Previous studies on DR have mainly focused on the health benefits produced by different restriction patterns, whereas comprehensive reviews of the role of gut microbiota during DR are limited. In this review, we discuss the effects of caloric restriction, fasting, protein restriction, and amino acid restriction from a microbiome perspective. Furthermore, the underlying mechanisms by which DR affects metabolic health by regulating intestinal homeostasis are summarized. Specifically, we reviewed the impacts of different DRs on specific gut microbiota. Additionally, we put forward the limitations of the current research and suggest the development of personalized microbes-directed DR for different populations and corresponding next-generation sequencing technologies for accurate microbiological analysis. DR effectively modulates the composition of the gut microbiota and microbial metabolites. In particular, DR markedly affects the rhythmic oscillation of microbes which may be related to the circadian clock system. Moreover, increasing evidence supports that DR profoundly improves metabolic syndrome, inflammatory bowel disease, and cognitive impairment. To summarize, DR may be an effective and executable dietary manipulation strategy for maintaining metabolic health, however, further investigation is needed to elucidate the underlying mechanisms.
... Hence, our current understanding of the effects of therapeutic fasting is mostly derived from observational studies [10][11][12]. ...
... Some studies have suggested that water-only fasting increases gut permeability in a colitis murine model [22] or in rats starved for 72 h [23]. An increase in gut permeability seems to be counteracted by a low calorie intake in humans [10] but also in animal models fed fasting-mimicking diets [22]. By contrast, a body of evidence indicates that caloric restriction in healthy conditions can improve intestinal barrier permeability in mice [24] or humans following a 4-week very-low-calorie diet [25]. ...
... Adaptation of the intestine to food reintroduction In general, studies in humans are focusing on the caloric restriction period but tend to neglect the food reintroduction phase. In a study on 15 men doing a 10-day fasting, the levels of inflammatory cytokines increased after food reintroduction, suggesting a reactivation of the postprandial immune response [10]. This is also observed in winter fasting in hibernating squirrels [30]. ...
Benefits of fasting and caloric restriction on host metabolic health are well established, but less is known about the effects on the gut microbiome and how this impacts renewal of the intestinal mucosa. What has been repeatedly shown during fasting, however, is that bacteria utilising host-derived substrates proliferate at the expense of those relying on dietary substrates. Considering the increased recognition of the gut microbiome's role in maintaining host (metabolic) health, disentangling host-microbe interactions and establishing their physiological relevance in the context of fasting and caloric restriction is crucial. Such insights could aid in moving away from associations of gut bacterial signatures with metabolic diseases consistently reported in observational studies to potentially establishing causality. Therefore, this review aims to summarise what is currently known or still controversial about the interplay between fasting and caloric restriction, the gut microbiome and intestinal tissue physiology.
... These results indicate that Lachnospiraceae may be involved in T2D [88]. A recent study observed a major decrease in the relative abundance of the Firmicutes, Lachnospiraceae, and Ruminococcaceae and an increase in Bacteroidetes and Proteobacteria when healthy subjects underwent ten-day, periodic, longterm fasting [77,89]. These changes in the microbiome were reversed after three months in healthy subjects [77,89]. ...
... A recent study observed a major decrease in the relative abundance of the Firmicutes, Lachnospiraceae, and Ruminococcaceae and an increase in Bacteroidetes and Proteobacteria when healthy subjects underwent ten-day, periodic, longterm fasting [77,89]. These changes in the microbiome were reversed after three months in healthy subjects [77,89]. However, it is also recognized that unhealthy individuals often have less diverse microbial environments [77,89]. ...
... These changes in the microbiome were reversed after three months in healthy subjects [77,89]. However, it is also recognized that unhealthy individuals often have less diverse microbial environments [77,89]. Therefore, the microbiome of unhealthy individuals, for example, those with T2D, may not have the same resilience to long-term fasting [77,89]. ...
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Type 2 diabetes (T2D) is a chronic condition that occurs in insulin-resistant people with reduced glucose uptake. It is contributed to and exacerbated by a poor diet that results in accumulation of adipose tissue, high blood sugar, and other metabolic issues. Because humans have undergone food scarcity throughout history, our species has adapted a fat reserve genotype. This adaptation is no longer beneficial, as eating at a higher frequency than that of our ancestors has had a significant effect on T2D development. Eating at high frequencies disrupts the circadian clock, the circadian rhythm, and the composition of the gut microbiome, as well as hormone secretion and sensitivity. The current literature suggests an improved diet requires meal consistency, avoiding late-night eating, low meal frequency, and fasting to increase metabolic health. In addition, fasting as a treatment for T2D must be used correctly for beneficial results. Early time-restricted eating (TRE) provides many benefits such as improving insulin resistance, cognitive function, and glycemic control. Alternate-day fasting (ADF), 5:2 fasting, and long-term fasting all have benefits; however, they may be less advantageous than early TRE. Therefore, eating pattern adjustments can be used to reduce T2D if used correctly.
... Another shared alteration in microbiota among both CR-treated humans and animals, is the increase in the genus Bacteroides [59, 63,66,79]. However, some studies reported opposite effects in an Alzheimer's disease mouse model, perhaps related to the genetic composition of this model [70,80] 89], Parabacteroides distasonis [71,90], and decreased Ruminococcaceae [62,63,91] and Coprococcus [19,91] (Table 1), which collectively correlate with the beneficial effects of CR. The human commensal F. prausnitzii, for example, constitutes one of the main butyrate producers [92], and is able to secrete anti-inflammatory cytokines and metabolites [93], collectively contributing to induction of an immunomodulated milieu [94,95]. ...
... The human commensal F. prausnitzii, for example, constitutes one of the main butyrate producers [92], and is able to secrete anti-inflammatory cytokines and metabolites [93], collectively contributing to induction of an immunomodulated milieu [94,95]. However, possibly due to the variations in baseline microbiota conformation, this trend was not reproducible in other studies [19,62]. ...
... In some cases, distinct microbiota changes were consistent among interventions. For example, multiple studies showed decreased Firmicutes/Bacteroidetes ratio and an increase in A. muciniphila, in CR spanning mild long-term restriction of 10% in daily energy intake [63,64], to very-low-calorie diet (VLCD) of about 800 kcal/d [102,103], and were also observed during a short-term fasting (250 kcal/d) for 10 days in healthy subjects [62]. In other cases, large inconsistencies were noted in microbiota responses to different CR regimens. ...
Caloric restriction (CR) and related time-restricted diets have been popularized as means of preventing metabolic disease while improving general well-being. However, evidence as to their long-term efficacy, adverse effects, and mechanisms of activity remains incompletely understood. The gut microbiota is modulated by such dietary approaches, yet causal evidence to its possible downstream impacts on host metabolism remains elusive. Herein, we discuss the positive and adverse influences of restrictive dietary interventions on gut microbiota composition and function, and their collective impacts on host health and disease risk. We highlight known mechanisms of microbiota influences on the host, such as modulation of bioactive metabolites, while discussing challenges in achieving mechanistic dietary-microbiota insights, including interindividual variability in dietary responses as well as other methodological and conceptual challenges. In all, causally understanding the impact of CR approaches on the gut microbiota may enable to better decode their overall influences on human physiology and disease.
... The health-promoting effects of long-term fasting (LF), lasting more than 4 days and up to several weeks, are increasingly documented (1)(2)(3). Our group has shown that LF improves cardiovascular (CV) risk factors such as hypertension even in medicated subjects, lipoprotein distribution, nonalcoholic fatty liver symptoms, inflammatory parameters, oxidative stress, and gut microbiota profiles (4)(5)(6)(7)(8)(9). A large observational study of 1,422 subjects underlined the safety, tolerability, and therapeutic efficacy of LF from 4 to 21 days (10). ...
... Finally, we will explore gut microbiota changes during LF. LF does not eliminate the gut microbiota, but elicits profound changes in its composition (6,40). In our recent study, changes in bacteria profiles caused by fasting were associated with serum glucose and fecal branched-chain amino acids (6), suggesting that the gut microbiota can influence fasting-induced changes in energy metabolism. ...
... LF does not eliminate the gut microbiota, but elicits profound changes in its composition (6,40). In our recent study, changes in bacteria profiles caused by fasting were associated with serum glucose and fecal branched-chain amino acids (6), suggesting that the gut microbiota can influence fasting-induced changes in energy metabolism. A more recent study even identified a bacteria which abundance correlates with serum concentrations of 3-hydroxybutyrate (41). ...
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Fasting provokes fundamental changes in the activation of metabolic and signaling pathways leading to longer and healthier lifespans in animal models. Although the involvement of different metabolites in fueling human fasting metabolism is well known, the contribution of tissues and organs to their supply remains partly unclear. Also, changes in organ volume and composition remain relatively unexplored. Thus, processes involved in remodeling tissues during fasting and food reintroduction need to be better understood. Therefore, this study will apply state-of-the-art techniques to investigate the effects of long-term fasting (LF) and food reintroduction in humans by a multi-systemic approach focusing on changes in body composition, organ and tissue volume, lipid transport and storage, sources of protein utilization, blood metabolites, and gut microbiome profiles in a single cohort. This is a prospective, single-arm, monocentric trial. One hundred subjects will be recruited and undergo 9 ± 3 day-long fasting periods (250 kcal/day). We will assess changes in the composition of organs, bones and blood lipid profiles before and after fasting, as well as high-density lipoprotein (HDL) transport and storage, untargeted metabolomics of peripheral blood mononuclear cells (PBMCs), protein persulfidation and shotgun metagenomics of the gut microbiome. The first 32 subjects, fasting for 12 days, will be examined in more detail by magnetic resonance imaging (MRI) and spectroscopy to provide quantitative information on changes in organ volume and function, followed by an additional follow-up examination after 1 and 4 months. The study protocol was approved by the ethics board of the State Medical Chamber of Baden-Württemberg on 26.07.2021 and registered at (NCT05031598). The results will be disseminated through peer-reviewed publications, international conferences and social media. Clinical trial registration [ ], identifier [NCT05031598].
... Subsequent individually tailored diets may maintain the benefits of fasting [14,15] even up to one year [13]. Previous studies on caloric restriction revealed changes in the microbiota and improvement of mucosal integrity [16][17][18][19][20]. Thus, dietary components and/or microbial metabolites may contribute to RA pathology via a disturbed intestinal barrier [21][22][23]. ...
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Rheumatoid arthritis (RA) synovitis is dominated by monocytes/macrophages with inflammatory patterns resembling microbial stimulation. In search of triggers, we reduced the intestinal microbiome in 20 RA patients (open label study DRKS00014097) by bowel cleansing and 7-day fasting (≤250 kcal/day) and performed immune monitoring and microbiome sequencing. Patients with metabolic syndrome (n = 10) served as a non-inflammatory control group. Scores of disease activity (DAS28/SDAI) declined within a few days and were improved in 19 of 20 RA patients after breaking the fast (median ∆DAS28 = −1.23; ∆SDAI = −43%) or even achieved remission (DAS28 < 2.6/n = 6; SDAI < 3.3/n = 3). Cytometric profiling with 46 different surface markers revealed the most pronounced phenomenon in RA to be an initially increased monocyte turnover, which improved within a few days after microbiota reduction and fasting. Serum levels of IL-6 and zonulin, an indicator of mucosal barrier disruption, decreased significantly. Endogenous cortisol levels increased during fasting but were insufficient to explain the marked improvement. Sequencing of the intestinal microbiota indicated that fasting reduced potentially arthritogenic bacteria and changed the microbial composition to species with broader metabolic capabilities. More eukaryotic, predominantly fungal colonizers were observed in RA, suggesting possible involvement. This study demonstrates a direct link between the intestinal microbiota and RA-specific inflammation that could be etiologically relevant and would support targeted nutritional interventions against gut dysbiosis as a causal therapeutic approach.
... This new dynamic balance kept steadily in the subsequent fasting time, documenting the metabolic switch. These results were consistent with previous reports that ketosis had been shown to reach a plateau after 4-5 days of prolonged CF [36,37]. The increased ATP calculated from glucose and BHB suggested fasting did not lead to energy deficiency even during the complete food deprivation. ...
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:Fasting shows great potential in preventing chronic diseases and has to be surmounted under some extraordinary circumstances. This study aimed to investigate the safety, time effects of metabolic homeostasis and health indexes during prolonged fasting. Thirteen participants were recruited to conduct a 10-day complete fasting (CF) in a controlled health research building under medical supervision including 3-day Baseline (BL), 10-day CF, 4-day calorie restriction (CR) and 5-day full recovery (FR). Body healthy status was assessed by surveying pulse, blood pressure, body weight (BW), blood glucose and ketones, body composition and nutritional and biochemistry indexes at different times. BW declined about 7.28 kg (−9.8%) after 10-day CF, accompanied by increased pulse and decreased systolic blood pressure, but there were no changes to the myocardial enzymogram. Body composition analysis showed fat mass was constantly lost, but lean mass could recover after CR. The energy substrate switch from glucose to ketone occurred and formed a stable dynamic balance between 3–6 days of CF. The lipid metabolism presented increased total cholesterol, LDL-C, ApoA1 and almost no changes to TG and HDL-C. Prolonged CF did not influence liver function, but induced a slight decrease of kidney function. The interesting results came from the marked increase of lipid-soluble vitamins and a significant decrease of sodium and chlorine. Adults could well tol-erate a 10-day CF. A new metabolic homeostasis was achieved. No vitamins but NaCl supplement should be considered. These findings provide evidence to design a new fasting strategy for clinical practice.
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Introduction: Chronic inflammatory diseases like rheumatoid arthritis (RA) and neurodegenerative disorders like Parkinson's disease (PD) have recently been associated with a decreased diversity in the gut microbiome, emerging as key driver of various diseases. The specific interactions between gut-borne microorganisms and host pathophysiology remain largely unclear. The microbiome can be modulated by interventions comprising nutrition.The aim of our clinical study is to (1) examine effects of prolonged fasting (PF) and time-restricted eating (TRE) on the outcome parameters and the immunophenotypes of RA and PD with (2) special consideration of microbial taxa and molecules associated with changes expected in (1), and (3) identify factors impacting the disease course and treatment by in-depth screening of microorganisms and molecules in personalised HuMiX gut-on-chip models, to identify novel targets for anti-inflammatory therapy. Methods and analysis: This trial is an open-label, multicentre, controlled clinical trial consisting of a cross-sectional and a longitudinal study. A total of 180 patients is recruited. For the cross-sectional study, 60 patients with PD, 60 patients with RA and 60 healthy controls are recruited at two different, specialised clinical sites. For the longitudinal part, 30 patients with PD and 30 patients with RA undergo 5-7 days of PF followed by TRE (16:8) for a period of 12 months. One baseline visit takes place before the PF intervention and 10 follow-up visits will follow over a period of 12 months (April 2021 to November 2023). Ethics and dissemination: Ethical approval was obtained to plan and conduct the trial from the institutional review board of the Charité-Universitätsmedizin Berlin (EA1/204/19), the ethics committee of the state medical association (Landesärztekammer) of Hessen (2021-2230-zvBO) and the Ethics Review Panel (ERP) of the University of Luxembourg (ERP 21-001 A ExpoBiome). The results of this study will be disseminated through peer-reviewed publications, scientific presentations and social media. Trial registration number: NCT04847011.
Experimental trials in organisms ranging from yeast to humans have shown that various forms of reducing food intake (caloric restriction) appear to increase both overall and healthy lifespan, delaying the onset of disease and slowing the progression of biomarkers of aging. The gut microbiota is considered one of the key environmental factors strongly contributing to the regulation of host health. Perturbations in the composition and activity of the gut microbiome are thought to be involved in the emergence of multiple diseases. Indeed, many studies investigating gut microbiota have been performed and have shown strong associations between specific microorganisms and metabolic diseases including overweight, obesity, and type 2 diabetes mellitus as well as specific gastrointestinal disorders, neurodegenerative diseases, and even cancer. Dietary interventions known to reduce inflammation and improve metabolic health are potentiated by prior fasting. Inversely, birth weight differential host oxidative phosphorylation response to fasting implies epigenetic control of some of its effector pathways. There is substantial evidence for the efficacy of fasting in improving insulin signaling and blood glucose control, and in reducing inflammation, conditions for which, additionally, the gut microbiota has been identified as a site of both risk and protective factors. Accordingly, human gut microbiota, both in symbiont and pathobiont roles, have been proposed to impact and mediate some health benefits of fasting and could potentially affect many of these diseases. While results from small-N studies diverge, fasting consistently enriches widely recognized anti-inflammatory gut commensals such as Faecalibacterium and other short-chain fatty acid producers, which likely mediates some of its health effects through immune system and barrier function impact.
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Only few studies document longer periods of fasting in large cohorts including non-obese participants. The aim of this study was to document prospectively the safety and any changes in basic health and well-being indicators during Buchinger periodic fasting within a specialised clinic. In a one-year observational study 1422 subjects participated in a fasting program consisting of fasting periods of between 4 and 21 days. Subjects were grouped in fasting period lengths of 5, 10, 15 and 20±2 days. The participants fasted according to the Buchinger guidelines with a daily caloric intake of 200–250 kcal accompanied by a moderate-intensity lifestyle program. Clinical parameters as well as adverse effects and well-being were documented daily. Blood examinations before and at the end of the fasting period complemented the pre-post analysis using mixed-effects linear models. Significant reductions in weight, abdominal circumference and blood pressure were observed in the whole group (each p<0.001). A beneficial modulating effect of fasting on blood lipids, glucoregulation and further general health-related blood parameters was shown. In all groups, fasting led to a decrease in blood glucose levels to low norm range and to an increase in ketone bodies levels (each p<0.001), documenting the metabolic switch. An increase in physical and emotional well-being (each p<0.001) and an absence of hunger feeling in 93.2% of the subjects supported the feasibility of prolonged fasting. Among the 404 subjects with pre-existing health-complaints, 341 (84.4%) reported an improvement. Adverse effects were reported in less than 1% of the participants. The results from 1422 subjects showed for the first time that Buchinger periodic fasting lasting from 4 to 21 days is safe and well tolerated. It led to enhancement of emotional and physical well-being and improvements in relevant cardiovascular and general risk factors, as well as subjective health complaints.
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Mexico is experiencing an epidemiological and nutritional transition period, and Mexican children are often affected by the double burden of malnutrition, which includes undernutrition (15.3% of children) and obesity (13.6%). The gut microbiome is a complex and metabolically active community of organisms that influences the host phenotype. Although previous studies have shown alterations in the gut microbiota in undernourished children, the affected bacterial communities remain unknown. The present study investigated and compared the bacterial richness and diversity of the fecal microbiota in groups of undernourished (n = 12), obese (n = 12), and normal-weight (control) (n = 12) Mexican school-age children. We used next-generation sequencing to analyze the V3–V4 region of the bacterial 16S rRNA gene, and we also investigated whether there were correlations between diet and relevant bacteria. The undernourished and obese groups showed lower bacterial richness and diversity than the normal-weight group. Enterotype 1 correlated positively with dietary fat intake in the obese group and with carbohydrate intake in the undernourished group. The results showed that undernourished children had significantly higher levels of bacteria in the Firmicutes phylum and in the Lachnospiraceae family than obese children, while the Proteobacteria phylum was overrepresented in the obese group. The level of Lachnospiraceae correlated negatively with energy consumption and positively with leptin level. This is the first study to examine the gut microbial community structure in undernourished and obese Mexican children living in low-income neighborhoods. Our analysis revealed distinct taxonomic profiles for undernourished and obese children.
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Evidence from the literature keeps highlighting the impact of mutualistic bacterial communities of the gut microbiota on human health. The gut microbita is a complex ecosystem of symbiotic bacteria which contributes to mammalian host biology by processing, otherwise, indigestible nutrients, supplying essential metabolites, and contributing to modulate its immune system. Advances in sequencing technologies have enabled structural analysis of the human gut microbiota and allowed detection of changes in gut bacterial composition in several common diseases, including cardiometabolic disorders. Biological signals sent by the gut microbiota to the host, including microbial metabolites and pro-inflammatory molecules, mediate microbiome–host genome cross-talk. This rapidly expanding line of research can identify disease-causing and disease-predictive microbial metabolite biomarkers, which can be translated into novel biodiagnostic tests, dietary supplements, and nutritional interventions for personalized therapeutic developments in common diseases. Here, we review results from the most significant studies dealing with the association of products from the gut microbial metabolism with cardiometabolic disorders. We underline the importance of these postbiotic biomarkers in the diagnosis and treatment of human disorders.
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Purpose of review: Since the early development of human societies, religious beliefs, and practices has been integral to their identity, culture, and social structure, traditions are influenced by the area, era, and culture wherein they developed. Some religions offer advice on behavioral and diet modifications as strategies to fortify the body, purify the spirit, and elevate consciousness. This review is an attempt to compare different practices, describe the health benefits and risks of fasting, and reconcile these age-old recommendations with practical modern life. Recent findings: Research to clarify and quantify the impact of these dietary modifications is challenging due to the variability in recommendations among various religions and in day-to-day practices. Most religions share common goals of well-being, body-mind integration, and spiritual attainment. Historically, the transformational power of fasting periods has been appreciated, but there is still much to discover about the underlying beneficial physiologic mechanisms of fasting in preventing and treating metabolic diseases.
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Ana M Valdes and colleagues discuss strategies for modulating the gut microbiota through diet and probiotics © Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to.
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The 2017 annual symposium organized by the University Medical Center Groningen in The Netherlands focused on the role of the gut microbiome in human health and disease. Experts from academia and industry examined interactions of prebiotics, probiotics, or vitamins with the gut microbiome in health and disease, the development of the microbiome in early-life and the role of the microbiome on the gut–brain axis. The gut microbiota changes dramatically during pregnancy and intrinsic factors (such as stress), in addition to extrinsic factors (such as diet, and drugs) influence the composition and activity of the gut microbiome throughout life. Microbial metabolites, e.g. short-chain fatty acids affect gut–brain signaling and the immune response. The gut microbiota has a regulatory role on anxiety, mood, cognition and pain which is exerted via the gut–brain axis. Ingestion of prebiotics or probiotics has been used to treat a range of conditions including constipation, allergic reactions and infections in infancy, and IBS. Fecal microbiota transplantation (FMT) highly effective for treating recurrent Clostridium difficile infections. The gut microbiome affects virtually all aspects of human health, but the degree of scientific evidence, the models and technologies and the understanding of mechanisms of action vary considerably from one benefit area to the other. For a clinical practice to be broadly accepted, the mode of action, the therapeutic window, and potential side effects need to thoroughly be investigated. This calls for further coordinated state-of-the art research to better understand and document the human gut microbiome’s effects on human health.
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Intermittent fasting (IF) protects against the development of metabolic diseases and cancer, but whether it can prevent diabetic microvascular complications is not known. In db/db mice, we examined the impact of long-term IF on diabetic retinopathy (DR). Despite no change in glycated hemoglobin, db/db mice on the IF regimen displayed significantly longer survival and a reduction in DR endpoints, including acellular capillaries and leukocyte infiltration. We hypothesized that IF mediated changes in the gut microbiota would produce beneficial metabolites and prevent the development of DR. Microbiome analysis revealed increased levels of Firmicutes and decreased Bacteroidetes and Verrucomicrobia Compared to db/db mice on ad-libitum (AL) feeding, changes in the microbiome of the db/db mice on IF were associated with increases in gut mucin, goblet cell number and villi length and reductions in plasma peptidoglycan. Consistent with the known modulatory effects of Firmicutes on bile acid (BA) metabolism, measurement of BAs demonstrated a significant increase of tauroursodeoxycholate (TUDCA), a neuroprotective BA, in db/db on IF but not in db/db on AL feeding. TGR-5, the TUDCA receptor, was found in neural cells of the retina primary ganglion cells. Expression of TGR5 did not change with IF or diabetes. However, IF reduced retinal TNF-α mRNA, which is a key downstream target of TGR-5 activation. Pharmacological activation of TGR5 using INT-767 prevented DR in a second diabetic mouse model. These findings support the concept that IF prevents DR by restructuring the microbiota towards species producing TUDCA and subsequent retinal protection by TGR5 activation.
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Metagenomics has transformed microbiology, but its potential has not been fully expressed yet. From computational methods for digging deeper into metagenomes to study designs for addressing specific hypotheses, the Segata Lab is pursuing an integrative metagenomic approach to describe and model human-associated microbial communities as collections of strains. Linking strain variants to host phenotypes and performing cultivation-free population genomics require large cohorts and meta-analysis strategies to synthesize available cohorts but can revolutionize our understanding of the personalized host-microbiome interface which is at the base of human health.
The common approach to the multiplicity problem calls for controlling the familywise error rate (FWER). This approach, though, has faults, and we point out a few. A different approach to problems of multiple significance testing is presented. It calls for controlling the expected proportion of falsely rejected hypotheses — the false discovery rate. This error rate is equivalent to the FWER when all hypotheses are true but is smaller otherwise. Therefore, in problems where the control of the false discovery rate rather than that of the FWER is desired, there is potential for a gain in power. A simple sequential Bonferronitype procedure is proved to control the false discovery rate for independent test statistics, and a simulation study shows that the gain in power is substantial. The use of the new procedure and the appropriateness of the criterion are illustrated with examples.
Serum immunoglobulin A (IgA) antibodies are readily detected in mice and people, but the mechanisms underlying the induction of serum IgA and its role in host protection remain uncertain. We report that select commensal bacteria induce several facets of systemic IgA-mediated immunity. Exposing conventional mice to a unique but natural microflora that included several members of the Proteobacteria phylum led to T cell-dependent increases in serum IgA levels and the induction of large numbers of IgA-secreting plasma cells in the bone marrow. The resulting serum IgA bound to a restricted collection of bacterial taxa, and antigen-specific serum IgA antibodies were readily induced after intestinal colonization with the commensal bacterium Helicobacter muridarum. Finally, movement to a Proteobacteria-rich microbiota led to serum IgA-mediated resistance to polymicrobial sepsis. We conclude that commensal microbes overtly influence the serum IgA repertoire, resulting in constitutive protection against bacterial sepsis.