Intermittent fasting is a lifestyle change that has, in the
past few years, been championed by popular culture. This eating
pattern involves alternating cycles of feeding and fasting.
In addition to benefits in weight loss, intermittent
fasting has also been connected to improved health outcomes,
including improved lifespan. While the practice has only recently
gained global traction, intermittent fasting is ancient
and has long been practiced globally. However, despite an
almost never ending supply of public information regarding
intermittent fasting, there is a shortage of evidence-based
support to guide this public health practice. In this video,
we will try to bridge this gap by explaining a major mechanism
behind some of the benefits of intermittent fasting, called
autophagy. Autophagy, literally "self-eating", is a blanket term
describing the different ways by which cells can degrade used up
materials. Although it may seem like the cells are eating
themselves, autophagy is actually a process that protect
cells from damage. Autophagy has an important role in determining
the lifespan of many organisms, and reduced autophagy is
associated with accelerated aging, and decreased longevity,
while stimulation of autophagy may have anti-aging effects.
However, just as autophagy can protect cells, it can also cause
harm. Before we get into that, let's discuss what happens
during autophagy. The body uses sensor proteins to detect the
levels of nutrients within its cells. In the absence of some
essential nutrients, like what might happen during a diet, these
sensor proteins send out a signal. This signal is carried to
several other proteins and converges on proteins called master
regulators. These master regulators then activate the
recycling process of autophagy so that the cell can recycle
some of its used up components. Autophagy begins when cell
contents are isolated in a type of wrap called the isolation
membrane. Next, several autophagy-related proteins, or
ATG proteins, associate with this membrane. The resulting
structure can then break down the sequestered contents into
simple components that can be released back into the cell,
where they are reused for nutrients and energy. Autophagy
plays an important role in determining your lifespan and
many diseases actually develop because of problems with
autophagy. In fact, autophagy dysfunction is documented in
Alzheimer's, Huntington's and Parkinson's disease. This is
because autophagy prevents the collection of toxic protein
aggregates, such as those observed in these
neurodegenerative diseases. As well, autophagy is associated
with the proper structuring of an important cell structure
called the mitochondria. This is vitally important since in most
complex animals, like humans, the mitochondria is important for
producing energy, and proper functioning is key to removing
harmful reactive oxygen species, which can cause inflammation.
Unfortunately, however, this important mechanism is sometimes
also exploited to cause harm. By inhibiting autophagy early on,
pre-cancer cells can shut down some of the body's quality
control mechanisms, allowing these abnormal cells to grow.
This allows the cells to continue dividing, eventually
forming a tumor. As a tumor grows, cells on the inside are
starved for nutrients and by reactivating autophagy, they can
ensure their survival. Since these tumor cells don't work
properly, they accumulate damaged products over time.
Normally, when cells accumulate too many defects, they activate
a controlled self destruction to prevent these defects from
spreading. However, by activating autophagy, the tumor
cells can move these damaged proteins, allowing them to
undergo further divisions. While autophagy has its downsides,
there's a growing body of evidence suggesting the role of
autophagy in preventing malignancy, infection,
neurodegenerative diseases, and in the slowing of aging. One way
we can activate autophagy is by caloric restriction, which is
defined as a 10-40% decrease in caloric intake, without a
reduction in dietary nutritional content. Caloric restriction has
been shown to prevent several age related diseases, including
high blood pressure and diabetes in humans. However, for many
people, caloric restriction is not sustainable. Fortunately, in
the past decade, an alternative eating regime, called
intermittent fasting, has fallen into the limelight. Intermittent
fasting comes in several different flavors, of which we
will discuss three. Complete alternate-day fasting involves
alternating days of fasting, when only energy lacking food or
beverages are consumed, followed by days of eating, when food and
beverages are consumed as one pleases. Modified fasting
regimes involve only consuming 20 to 25% of your daily energy
needs. For people with light to moderate activity levels, this
means around 750 calories per day for men and 550 calories a
day for women. This is the basis for the 5:2 diet, where
the energy restriction occurs only two days a week. Time
restricted feeding involves eating as you please during
specific timeframes and fasting from energy containing food and
drink for the remainder of the day. Most commonly, this
involves eating for eight hours a day and fasting for the
remaining 16. In all cases, these have been associated with
weight loss and reduction of many markers of disease, such as
elevated blood insulin and blood glucose levels. With that said,
you might be wondering, "Well, which is best?". And the answer to
that depends on you. In order to achieve long term metabolic
improvements, it's important to select a diet to which you can
make a long term commitment. Before starting any diet,
It is important to consult first with your doctor. This is
especially important if you have pre-existing health conditions
such as diabetes, low blood pressure, and issues with blood
sugar regulation or pregnancy.