fad has a reputation in the u.s. there's
a multi-billion dollar industry
dedicated to convincing you to spend a
bunch of money to get rid of facts but
that isn't an enemy we spend so much
time and money trying to eliminate it
that we never give that a proper chance
to amaze us our fad is an evolutionary
advantage allowing us to store a lot of
energy and relatively dense packages
like we talked about in the last episode
gram for gram that is the most efficient
way to store energy in our bodies and
it's not just a storage center it's an
ever changing organ that contributes to
our well-being in today's episode we'll
learn about what our fat does and
hopefully walk away a little more
excited that it exists as a quick
disclaimer we're not talking about
dietary fats like the one from oil
butter or meats this video focuses on
fat as adipose tissue a collection of
different cells that we have in
different locations in our bodies this
type of tissue is made of endothelial
cells a few immune cells but mostly a
special type of cell called adipocytes
in every gram of adipose tissue you'll
find anywhere from one to two million
adipocytes here's what I think is so
cool that cells aren't passive
structures adipocyte has site in the
name so we know that it's a living
metabolizing cell and if we zoom in on
it we can see cell structures like a
nucleus with DNA in it but most of its
body is a storage site for lipid the
energy storage we're so interested in we
have about 30 billion fat cells and when
we store some excess energy the cells
will grow in size then if they can't
grow anymore but you still need to store
energy you'll grow new fat cells so you
can store more energy now when we see
pictures of body fat it's usually shown
as a lumpy yellow tissue and it's true
that is a type of fat that exists but
that's not the only type of fat we have
the type of fat you're used to seeing is
probably visceral fat visceral just
means that it's in the abdomen
surrounding your internal organs this is
what's often called belly fats although
there's a little more to it than that we
have another layer of fat underneath our
skin called subcutaneous fat sub 4 under
cutaneous for skin if you have skin this
stuff is under it that means the skin
under but chest thighs and yep the
abdomen subcutaneous fat is used mostly
for energy storage and some but not a
ton of insulation we keep that in a few
other sneaky spots too some fat has more
of a mechanical purpose like the fat
that supports the eyes and the fat pads
that cushion the heels and we have that
between some of our skeletal muscle
fibers it doesn't matter if you have a
lot of body fat or if you're very lean
everyone has fat in their muscles fun
fact you can see intramuscular fat as
the marbled and a cut of steak along
with the visceral and subcutaneous fat
these locations of fat make up your
white adipose tissue that adipocyte we
showed you earlier was an example of
white adipose tissue but you also have a
separate type called brown adipose
tissue which mostly exists so we can
create body heat its cell looks a little
different check out how it has multiple
lipid droplets compared to white
adipocytes but it's also got quite a few
more mitochondria and it's surrounded by
blood vessels and nerves so it can heat
up the blood brown fat is especially
useful when you're a baby
newborns can't shiver for warmth so they
rely on brown fat to stay toasty okay
babies are useless as you get older
though you develop other strategies to
stay warm like shivering or just putting
on a hoodie this brown adipose tissue
was more useful for our ancestors who
were exposed to the elements plus this
tissue is only found in mammals so other
animals use it to help them keep warm
too although there are some
circumstances where we will use it as
adults like if we're knocked out during
general anesthesia and our bodies detect
low body temperature you're definitely
not putting on a hoodie then on account
of you know being knocked out and
everything
now for a long time people thought that
was a passive energy storage reservoir
it was a useful source of emergency
calories but otherwise it didn't serve
any larger function these days we know
that's not true
especially when we consider its role in
the endocrine system this is a system
that handles hormones including the sex
hormones like estrogen and testosterone
but also other hormones that have
effects on parts of the body that aren't
that before scientists name any of the
specific hormones they suspected there
might be something floating around the
blood that signaled energy levels to the
central nervous system one of the first
big moments in this concept was back in
the early 70s with an experiment on
obese and diabetic mice see scientists
can breed mice with different genetic
profiles or genotypes that results in
predictably physically different mice or
phenotypes of mice in this case a tweak
in the ob gene part of the mouse's
genotype results in an obese Mouse its
phenotype this makes sure that the test
subjects are as consistent as possible
during the experiment mice were stitched
together in an experimental condition
called parabiosis meaning certain
aspects of their Anatomy including their
circulatory systems or connected this
style of experiment used to be more
common in the 60s and 70s and it led to
some big breakthroughs in our
understanding of hormones and in the
immune system the experimenters at the
time set up four para biotic scenarios
an obese Mouse joins to a normal healthy
Mouse a diabetic Mouse joins to an obese
Mouse now Visa women obese and finally
normal with normal as controls it was
common for some of the mice to die
during the experiment and in the
diabetic obese combo the obese Mouse
tended to get hypoglycemia and died but
most of the mice and the other
conditions survived meaning almost all
of the obese obese combinations made it
and both partners gained weight quickly
on the other hand the obese normal
combinations also survived and gained
weight but to a lesser degree than the
Oh
obese mice the researchers that meant
that the normal mice were secreting some
kind of hormone that regulates food
consumption into the bloodstream of
their obese partner now every hormone
needs a receptor and this hormones main
source of receptors was in the
hypothalamus a portion of the brain that
signals the release of a bunch of other
hormones - now here's the big payoff
that para biotic Mouse study gave
researchers a substance to look for what
they called a satiety factor that OB
gene that resulted in obese mice had
also been shown to make a specific
protein and in 1994 that hormone was
discovered and named leptin it's a
hormone released from adipocytes that
tells our bodies we have enough energy
and we're not starving adipocytes will
give off different amounts of leptin
depending on how much fat mass we have
our nutritional status plus a few other
factors leptin x' main job is to signal
that you have enough energy stores not
excess energy stores so when you don't
eat enough or you're losing weight lower
leptin levels are a signal to your brain
that it should eat more that's one of
the reasons that diets are largely
pointless your body will literally
adjust to tell you to eat more leptin is
involved in a few other things too like
immune function regulation and bone
development and leptin isn't the only
hormone that fat tissue makes it also
makes a hormone that helps regulate
blood sugar called adiponectin and a
bunch of enzymes that can modify steroid
hormones like estrogen and testosterone
that's especially useful if you're a
person with ovaries and in menopause up
to a hundred percent of circulating
estrogen comes from adipose tissue for
postmenopausal women as if the energy
stored and hormone production wasn't
enough fat is also a useful source for
stem cells stem cells can become other
types of cells and show promise as
treatments in the future and in the last
few years scientists around the world
have figured out ways to take that
tissue and turn them into stem cells
this is called induced pluripotent C if
you take a mature cell and transform it
into a cell that can become
their cell types that's great since we
have plenty of adipose tissue in our
bodies and it's easily accessible with a
little bit of liposuction this also
makes sure that the stem cells are
compatible with the recipients immune
system since they came from the
recipients body in the first place but
this is all relatively new science and
there's ongoing research to figure out
best practices for fat derived stem
cells plus there's still more to learn
about fats role in the endocrine system
- my goal with this episode was to show
you that fat is incredibly valuable to
our bodies fat is part of what makes us
human and it's worth celebrating how
cool this organ is thanks for watching
this episode of seeker human and
appreciating the body with us
I'm Patrick Kelly