When We Lose Weight, Where Does It Go?

When we lose weight, it doesn't just vanish. Learn how our bodies shrink fat cells in this episode of BrainStuff.

Learn more about your ad-choices at https://www.iheartpodcastnetwork.com

See omnystudio.com/listener for privacy information.

Episode Transcript

Speaker 1 (00:02):
Welcome to brain stuff from how stuff works. Hey, brain stuff,
Lauren Vogel Bomb here. For many of us humans, our
body size and shape our things in flux from one
month to the next, depending on a host of factors
both within and without our control. Our genes might be
a little tighter or a little looser. Our question of
the day is when we lose weight, where does that

(00:24):
lost weight go. The short answer is that our bodies
convert molecules in fat cells to usable forms of energy,
thus shrinking the cells. But getting this to happen isn't
just about sweating to the oldies or however you prefer
to work out. Understanding how our bodies perform this tummy
trimming trick requires a little more detail. We know that

(00:44):
weight loss hinges on burning calories. Calories are the measure
of the potential energy in the food you eat, in
the form of fats, proteins, and carbohydrates. If our bodies
were cars, energy would be the gas that keeps everything running.
Lounging in front of the television is like cruising the strip,
while sprinting around a track is more like drag racing
at maximum speeds. In short, more work means more energy

(01:06):
is needed, the body uses some of the calories we
ingest to digest that very food. Once the food is
broken down into its respective parts of carbohydrates, fats, and proteins,
it either uses the remaining energy or converts to fat
for storage in fat cells and as doctor who fans know,
fat cells live in adipose tissue, which basically acts like
an internal gas station, storing away fuel reserves. To lose weight,

(01:29):
you must burn more calories or energy than you consume
to start using up that fuel reserve. Essentially, if you're
not ingesting enough calories to fuel your additional work, your
body must pull from fat stores. According to the law
of conservation of mass, matter is neither created nor destroyed,
but it may alter its form through chemical reaction. Essentially,
that tells us that while we lose mass in our

(01:51):
bodies by burning up fat, it doesn't just disappear, It
simply changes form. When we eat, the glucose and other
sugars harnessed from carbo high drates are the first things
our bodies use as fuel stores. The liver stores the
glucose in the form of glycogen and releases it into
the blood stream as necessary to keep our bodies trucking along.
Think of your blood stream as an interconnected conveyor belt

(02:12):
that takes necessary nutrients to the body parts that need them.
Once that glucose runs out, fat takes over. Harnessing energy
by burning fat is referred to as catosis. It works
like this. Hormones regulating our blood sugar levels activate an
enzyme in the blood vessels of fat tissue called liepace.
Liepase ignites fat cells to release macro molecules called triglycerides,

(02:34):
which are what makes fat cells fat. Triglycerides are made
up of glycerol and three fatty acid chains. When they
receive the signal from liepace to exit the fat cells,
the triglycerides break up into their respective components and enter
the bloodstream for use. The liver snatches up the glycerol
to break it down for energy, and some of the
fatty acids move to the muscles that can form them

(02:55):
for energy as well. The action of breaking down triglycerides
into usable energy is old like polysis. Once the components
of the glycerol and fatty acids are inside are muscle
or liver cells, organelles called mitochondria shuffle and reshuffle those
compounds to harness their potential energy, sort of like a
furnace burns would the mitochondria breakdown and recombine those components

(03:17):
of our fat cells and produce heat, water, carbon dioxide,
and a denisine triphosphate or a t P. A t
P halls potential energy and its molecular bonds for use.
When we exercise, like intercellular carb loading, the water exits
our bodies as sweat and urine, and we exhale the
carbon dioxide. Now that the body has relieved fat cells

(03:38):
of some glycerol and fatty acids, the cells get smaller,
and so cell by cell, our body shape changes. Today's
episode was written by Christine Conger and produced by Tyler Claying.
To hear more from Christin check out her podcast Unladylike,
available wherever you listen to podcasts, and, of course, to

(03:59):
get the skinny on this and lots of other topics,
visit our home planet, how Stuff Works dot com. H