Last week, on Chinese New Year’s eve, my brother
and I chatted online. As usual, our
friendly chat quickly deteriorated into relentless teasing of each other. Of course, as always, he started calling me “fatty,”
(and, yes, he is the good looking one in the family), which triggered me
calling him all kinds of names that I knew he hated. The perpetual fun between siblings!
However, my brother’s comments on my weight did
make me think about the weight and obesity.
As with skincare, obesity is directly related to lifestyle. In my past post, I’ve discussed the relationship
between skincare and the skin microbiota population. This post is about the obesity and gut
microbiota population.
Nobel laureate Lidberg postulated that the human
body is a super organism that consists of human cells and symbiotic
microorganisms cells of large number. Through the metabolic capacities encoded
by both the human and symbiotic microorganisms genes, drugs and food entering
the human body are processed and transformed, affecting human health.
Gut microbiota population is the largest
symbiotic microorganism group inside the human body, mainly living in the large
intestine and consisting of 1-2 kg of cells. Members of the gut microbiota
population can produce a variety of metabolites that, when entering the human
body, have positive or negative impacts. Metabolites produced by
beneficial bacteria include nutrients such as vitamin K, short-chain fatty
acids, and anti-inflammatory, analgesic and antioxidant substances. Beneficial bacteria also form a biofilm on the
intestinal mucosa, which has a protective effect on the intestinal barrier. Harmful
gut microbiota population members are usually pathogens or spoilage bacteria. The toxic
substances they produce can be categorized into three groups: cytotoxins which
are toxic to cells, genetic toxins which cause genetic mutations and immunotoxins
which disrupt
the immune system. If the intestinal barrier function is impaired, various
types of toxins produced by bacteria may enter the blood, and break down the
immune system, resulting in various diseases.
The latest scientific evidence suggests that gut
microbiota population may play a critical role in the development of obesity. Experiments show that germ free animals would
not suffer from obesity even when they are fed a high-fat diet (Bäckhed, F., et al., PNAS, 2007. 104 (3): p.
979-984). The gut microbiota population may
mediate the onset of obesity through the following mechanisms: first, they can
ferment dietary fiber, which a host cannot utilize otherwise, into short-chain
fatty acids for the host to absorb and use as an energy source. Thus, the gut microbiota population can help
a host to utilize healthy diet more efficiently and in turn reduces the host’s
food intake through a negative feedback loop.
More importantly, the gut microbiota population
can directly participate in the regulation of host gene expression involved in
fat metabolism. The product of fiaf
gene is a starvation-induced transcriptional factor and a regulatory protein promoting fatty acids oxidation. The gut microbiota
population can inhibit fiaf
expression, therefore impeding the proper function of host's genes related to fatty acid oxidation. When fiaf is not functioning, the host cannot
effectively utilize the stored fat, even in the state of starvation (Bäckhed,
F., et al., PNAS, 2004. 101 (44): p. 15718-15723). This might explain the paradoxical observation that obese
person does not tolerate hunger well, since the gut microbiota population
deterioration that caused obesity also inhibits fatty acid oxidation.
In another pathway, the gut
microbiota population can also increase the expression level of the genes related
to fat synthesis in liver and promote the de
novo synthesis of triglycerides. Therefore,
the gut microbiota population can directly participate in and to some extent
control the host's fat metabolism and turn the host into a highly efficient fat
synthesis and storage machine. Since the proper structure and function of gut
microbiota population is intrinsic to fat metabolism, it is imperative to
restore and maintain a healthy gut microbiota population; if the composition of
the gut microbiota population cannot be effectively reinstated, it will be
difficult to restore the distorted state of a host's energy metabolism to a normal
state, thus the stored fat in an obese person's body cannot be effectively
broken down, while food craving during a diet will be hard to overcome.
Gut microbiota population can be changed through
diet. It is known that fiber rich diets
can graduately cause shifting of a gut microbiota population from a harmful
population to a more beneficial population.
So do start chomp on those leafy greens and fruits. They will make you feel great and look
fabulous literally by changing your genes.
Thanks for reading.
Connie
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