What Happens To Your Body When You Fast?

What Happens To Your Body When You Fast?

August 21, 2019 100 By William Morgan


Some religious groups require followers to
fast for many hours a day, and continue that
fast for days or weeks! Isn’t not eating for
16 hours a day every day dangerous?
Bom dia earthlings, thanks for stopping by
DNews, I’m Trace. The Holy Month of Ramadan
is wrapping up this week, and those Muslims
who have been fasting for 15 hours a day or
more will be able to enjoy food anytime again.
It’s not just Muslims who fast, Christians,
Jews, Confucians, Hindus and other religions
have followed the practice for 1000s of years.
Non-religious folks fast too, usually for
medical or dietary reasons. For some people,
the idea of abstaining from food while the
sun is in the sky is unfathomable, and they
might feel that’s it’s unsafe! So science
is here to demystify some fasting myths.
A person is considered to be “fasting” if
they’ve abstained from a meal for 8-12 hours,
so if you think about it, most people fast
every night — and BREAK their fast in the
morning. That’s where the term BREAK-FAST
came from. Fasting is a completely normal
part of being an animal on the planet earth.
Many organisms eat only once a day or less,
especially those eating high-calorie foods
like meats. Cold-blooded carnivores, like
snakes, can go DAYS between meals, warm blooded
carnivores, like wolves or coyotes, hunt daily.
Like the coyote, humans are built to be able
to fast for a short period. A day or so isn’t
going to hurt you and some studies have shown
short-term fasts can extend lifespan, boost
immunity and mental function, and so on. We
did a whole video about that last Ramadan.
A study published last month in Cell Stem
Cell found that fasting two to four days at
a time can cause a reduction in white blood
cells, which is actually a GOOD thing. See,
the cells that are killed off are the older
or damaged immune cells, and when the body
rebounds, it uses stem cells to create brand
new, healthy ones.
Long-term fasting, on the other hand, is a
whole other beast. When humans fast, our bodies
go through a very predictable schedule. Our
bodies are great at squirreling away energy
in the forms of fats and sugars. But, like
coyotes, ideally, we’d eat every day or so
to replenish those reserves. After 24-48 hours
of fasting, the glycogen reserves stored in
our liver and muscles — basically carbohydrates
— are empty. After two days, the body’s figured
out that it needs to feed on itself, and will
begin breaking down muscle and fat tissues.
Obviously, water is important too. 72 hours
without water is dangerous, so while straight
food fasting isn’t so bad for you in this
short a burst, 72 hours is the beginning of
medical dehydration. So drink water, no matter
what.
Some of you might already be Yahoo-ing to
get the lowdown on a fasting diet, but the
problem is, we don’t REALLY work that way.
When you fast, you lose a few pounds right
away, but it’s mainly liquid weight, and it
will be replaced as soon as you eat again.
Which is another thing, Researchers at Cornell
asked college students to fast for 18 hours,
and then offered them a buffet-style meal
(not unlike Iftar, or community meals after
sundown during Ramadan). THe most popular
foods were those that were high in calories,
carbs and starches, because our cells don’t
know if we’re EVER GOING TO EAT AGAIN! Therefore,
they turn on the cravings for carbs and fats
which might fend off long-term starvation.
But that’s silly, you know you’re going to
eat again! Don’t listen to your reptilian
brain! Ideally, a human coming off of a fast
would eat vegetables and fruits. Lean meats
and a few carbs can be part of the meal, but
not a big part.
Ultimately, fasting puts stress on the systems
of your body, but low-level stress isn’t going
to hurt you, and it might build up the systems
— similar to how exercise stress builds muscles.
Fasting isn’t dangerous or deadly, as long
as it’s done properly and in partnership with
a healthy diet and exercise.
If you decide to fast, let us know why and
how you’ve done it! We’re curious.
You can fill us in on your journey in the
comments, or send us a tweet at-DNews or me
at-TraceDominguez. Speaking of journeys, if
you want to know how MSL Curiosity got to
Mars, and what the heck it’s doing up there
come to our SpaceOut on July 30th at 4pm Pacific
Time! We’re getting experts from NASA JPL
who actually work with the rover on Mars every
sol — that’s Martian for Day! See you’re
learning already! Get over there and RSVP.
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