In recent years, numerous studies have suggested that intermittent fasting - abstaining or reducing food and drink intake periodically - can be good for us, making it one of the most popular diet trends worldwide.
One
of the most well-known intermittent fasting diets is the 5:2
Fast Diet - a plan that involves eating the recommended calorie
intake for 5 days a week but reducing calorie intake to 25% for the remaining 2
days - to 500 calories a day for
women and 600 a day for men.
According
to Dr. Michael Mosley - author of The Fast Diet books - this
eating plan can not only help people lose weight, but it offers an array of
other health benefits.
"Studies
of intermittent fasting show that not only do people see improvements in blood
pressure and their cholesterol levels,
but also in their insulin sensitivity,"
he adds.
In
June 2014, for example, Medical News Today reported on a study
suggesting periodic fasting - defined in the study as 1 day of water-only fasting
a week - may reduce
the risk of diabetes among people at high risk
for the condition.
Another
study, conducted by Dr. Valter Longo and colleagues from the University of
Southern California (USC) in Los Angeles, found longer periods of fasting - 2-4
days - may even "reboot"
the immune system, clearing out old immune cells
and regenerating new ones - a process they say could protect against cell
damage caused by factors such as aging and chemotherapy.
But
what are the mechanisms underlying the suggested health benefits of fasting?
The potential benefits
of intermittent fasting
Since
the body is unable to get its energy from food during fasting, it dips into
glucose that is stored in the liver and muscles. This begins around 8 hours
after the last meal is consumed.
When
the stored glucose has been used up, the body then begins to burn fat as a
source of energy, which can result in weight loss.
As
well as aiding weight loss, Dr. Razeen Mahroof, of the University of Oxford in
the UK, explains that the use of fat for energy can help preserve muscle and
reduce cholesterol levels.
"A
detoxification process also occurs, because any toxins stored in the body's fat
are dissolved and removed from the body," he adds, noting that after a few
days of fasting, higher levels of endorphins - "feel-good" hormones -
are produced in the blood, which can have a positive impact on mental
well-being.
As
mentioned previously, the study by Dr. Longo and colleagues suggests prolonged
fasting may also be effective for regenerating immune cells.
"When
you starve, the system tries to save energy, and one of the things it can do to
save energy is to recycle a lot of the immune cells that are not needed,
especially those that may be damaged," Dr. Longo explains.
In
their study, published in the journal Cell Stem Cell, the team
found that repeated cycles of 2-4 days without food over a 6-month period
destroyed the old and damaged immune cells in mice and generated new ones.
What
is more, the team found that cancer patients who fasted
for 3 days prior to chemotherapy were protected against immune system damage
that can be caused by the treatment, which they attribute to immune cell
regeneration.
"The
good news is that the body got rid of the parts of the system that might be
damaged or old, the inefficient parts, during the fasting," says Dr.
Longo. "Now, if you start with a system heavily damaged by chemotherapy or
aging, fasting cycles can generate, literally, a new immune system."
With
the potential health benefits of fasting widely hailed by nutritionists
worldwide, it is no wonder many of us are putting our love of food to one side
in order to give it a try.
But
intermittent fasting isn't all bells and whistles, according to some
researchers and health care professionals, and there are some people who should
avoid the diet altogether.
