The latest study to
explore the impact of fasting on the human body concludes that it increases
metabolic activity more than previously realized and may even impart anti-aging
A recent study takes a
look at how fasting influences metabolism.
Studies have shown that
intermittent fasting can help certain people lose weight.
are still debating exactly how effective fasting can be for weight loss, new
research hints at other benefits.
In rats, for instance,
studies show that fasting can increase lifespan.
evidence of this in humans has yet to be seen.
The most recent study —
which the authors have now published in the journal Scientific Reports — takes
a fresh look at fasting in humans and provides new insight.
studies have shown that caloric restriction and fasting have a prolonging
effect on lifespan in model animals,” says first study author Dr. Takayuki
Teruya, “but the detailed mechanism has remained a mystery.”
scientists at the Okinawa Institute of Science and Technology Graduate
University in Japan examined its impact on metabolism.
By understanding the
metabolic processes involved, the team hopes to find ways of harnessing the
benefits of fasting without the need to go without food for prolonged periods.
To investigate, they
fasted four volunteers for 58 hours. Using metabolomics, or the measurement of
metabolites, the researchers analyzed whole blood samples at intervals during
the fasting period.
What happens during
As the human body is
starved of food, there are a number of distinct metabolic changes that occur.
Normally, when carbohydrates
are readily available, the body will use them as fuel. But once they are gone,
it looks elsewhere for energy. In a process called gluconeogenesis, the body
derives glucose from noncarbohydrate sources, such as amino acids.
Scientists can find evidence
of gluconeogenesis by assessing the levels of certain metabolites in the blood,
including carnitines, and butyrate.
As expected, after
fasting, the levels of these metabolites were present in the participants’
blood. However, the scientists also identified many more metabolic changes,
some of which surprised them. For instance, they saw a marked increase in
products of the citric acid cycle.
The citric acid cycle
happens in mitochondria, and its function is to release stored energy. The hike
seen in the metabolites associated with this process means that the
mitochondria, the fabled powerhouses of the cell, are thrust into overdrive.
finding was an increase in levels of purine and pyrimidine, which scientists
had not yet linked to fasting.
These chemicals are a
sign of increased protein synthesis and gene expression. This suggests that
fasting causes cells to switch up the type and quantity of proteins that they
need to function.
Higher levels of purine
and pyrimidine are clues that the body might be increasing levels of certain
antioxidants. Indeed, the researchers noted substantial increases in certain
antioxidants, including ergothioneine and carnosine.
In an earlier study,
the same team of researchers showed that, as we age, a number of metabolites
decline. These metabolites include leucine, isoleucine, and ophthalmic acid.
In their latest study,
they showed that fasting boosted these three metabolites. They explain that
this might help explain how fasting extends lifespan in rats.
In all four subjects,
the researchers identified 44 metabolites that increased during fasting, some
of which increased 60-fold.
Of these 44, scientists
had linked just 14 to fasting before. The authors conclude that
“[c]ollectively, fasting appears to provoke a much more metabolically
active state than previously realized.”
“These are very
important metabolites for maintenance of muscle and antioxidant activity […].
This result suggests the possibility of a rejuvenating effect by fasting, which
was not known until now.”
The scientists believe
that a hike in antioxidants might be a survival response; during starvation,
our bodies can experience high levels of oxidative stress. By producing
antioxidants, it might help avoid some of the potential damage caused by free
Next, they want to
replicate the results in a larger sample. They also want to identify possible
ways of harnessing the beneficial effects of fasting and find out whether they
can trigger the effects of caloric restriction without having to restrict
Although it will be
some time before we can reap the benefits of fasting without the effort, the
current findings provide further evidence of the health benefits of fasting.