- Evidence
is building that a healthy, diverse gut microbiome can benefit health.
- Studies have shown that people and
animals with obesity often have a less diverse microbiome than those of a
healthy weight.
- Now, research from China suggests that
intermittent energy restriction (IER) — which involves eating normally on
some days and eating a very restricted diet, or fasting, on others — not
only helps people lose weight but may also alter their microbiome.
- This small, observational study shows
only an association between weight loss and microbiome changes, rather
than any causative effects.
Recently, research has found increasing evidence of the potential
effects of the human microbiome . on
our health.
The microbiome consists of bacteria, archaea, viruses and eukaryotic
microbes that live in and on our bodies. A healthy adult will house around 1000
different species of bacteria, the majority of which are in the gut.
In most people, the core microbiota . remain stable
throughout adulthood, but the gut microbiota differs between different people. It is
affected by body mass index . (BMI) level, exercise
frequency, lifestyle, cultural and dietary habits, and antibiotic use.
Studies . in people with
obesity have found that they tend to have a less diverse gut microbiome, and the balance of species is different from
that of leaner people. Other studies . have
suggested that the ease with which people lose weight on diets is linked to the composition of
their gut microbiome. However, research . has
not yet revealed a consistent association between gut microbiota and obesity.
A meta-analysis of studies . found that weight
loss was associated with an increase in microbiome diversity and a reduction in
intestinal permeability.
Now, a small
study from China has suggested that intermittent energy restriction (IER), as
well as helping people with obesity to lose weight, may alter their gut
microbiota.
The study is published in Frontiers
in Cellular and Infection Microbiology.
The types of gut bacteria affected by weight loss
As part of the study, the researchers recruited 25 people with a body
mass index (BMI) of between 28kg/m2 (classed as overweight) and
45kg/m2 (classed as severely obese). None of the participants
had any other uncontrolled health conditions.
To start, they ate a regular diet for four days, and the researchers
recorded the energy content of this as their baseline daily intake. For the
rest of the study, the researchers interspersed the days of regular baseline
energy intake with days where the participants had severely restricted energy
intake formulated by a clinical dietitian.
The researchers collected the participants’ blood and fecal samples at
the beginning, midpoint, and end of phases II (highly-controlled fasting) and
phase III (less-controlled fasting) during the two months the study was
conducted. They also recorded their body weight, waist circumference, body fat, systolic blood pressure, and diastolic blood pressure at each time point.
During the
study, participants lost, on average, 7.8% of their body weight. And at the end
of phase II, their gut microbial diversity had increased from the baseline.
However, at the end of phase III, there was no significant difference from the
start of the study.
There were also some changes in the species making up the gut
microbiota, with a decrease in Escherichia coli and an increase
in Faecalibacterium
prausnitzii, Parabacteroides distasonis, and Bacteroides uniforms.
How gut bacteria changes affect health
Kelsey Costa, a registered dietitian and nutrition consultant
for the National Coalition on Healthcare, who was not involved in the study,
explained how these changes in gut bacteria might affect health:
“F.
prausnitzii is one of the most abundant bacteria in the gut and is generally
associated with good health and immunity. […] P. distasonis is associated
with breaking down carbohydrates and producing useful metabolites. This
bacteria is known to thrive in a diet rich in fiber. B. uniformis is known to
have anti-inflammatory properties and plays a role in processing complex sugars
in our diet.”
“The
alteration in gut microbe abundance induced by the diet is potentially
beneficial, as these changes could help modulate metabolic and immune
processes, though additional research is needed to fully understand the
long-term effects,” she added.
The researchers noted that these changes were associated with
significant reductions in the activity of brain regions implicated in the
regulation of appetite and addiction. However, they do not explain what effect
these changes are likely to have on appetite.
More evidence of gut-brain links
In a press release, co-author Dr. Xiaoning Wang from the Institute
of Geriatrics of the PLA General Hospital stated:
“The gut
microbiome is thought to communicate with the brain in a complex,
two-directional way. The microbiome produces neurotransmitters and neurotoxins,
which access the brain through nerves and the blood circulation. In return, the
brain controls eating behavior, while nutrients from our diet change the
composition of the gut microbiome.”
As an observational study, this research cannot show a causal
relationship between IER, weight loss, and the gut microbiome, but it does
provide more evidence of a link. The researchers suggest that long-term dietary
intervention should be used to maintain weight loss and further clarify the
relationship between the gut microbiome and the brain, and Costa agreed.
“Future research should aim to address the exact process through which
the gut microbiome interacts with the brain in obese individuals, specifically
during weight loss, including the identification of crucial gut microbiome
components and brain regions that contribute to successful weight loss and
maintenance of a healthy weight,” she told MNT.
She also gave general advice about how to look after your microbiome:
“The gut
microbiome is a complex ecosystem, and its relationship with obesity is not
fully understood. It’s thought that balance and diversity of gut bacteria may
be more important than the presence or absence of specific species.”
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