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What Really Happens When Body Fat is Burned?
By Tom Venuto, NSCA-CPT, CSCS
www.BurnTheFat.com
Earlier this week someone in our discussion forum wrote, "I haven't "LOST" any
fat... I know EXACTLY where it went! I got a chuckle out of
that because I "got" the joke, but truth is, most people really
don't know how fat cells work, how the fat burning process takes place
or where the fat goes when it's burned. It's actually quite a complex
biochemical process, but I'll explain it as simply as possible, so by
the end of this article, you'll be a "fat burning" expert!
When you "lose" body fat, the fat cell (also called an adipocyte)
does not go anywhere or "move into the muscle cell to be burned.
The fat cell itself, (unfortunately) stays right where it was - under
the skin in your thighs, stomach, hips, arms, etc., and on top of the
muscles - which is why you can't see muscle "definition" when
your body fat is high.
Fat is stored inside the fat cell in the form of triaglycerol.
The fat is not burned right there in the fat cell, it must be liberated
from the fat cell through somewhat complex hormonal/enzymatic pathways.
When stimulated to do so, the fat cell simply releases its contents (triaglycerol)
into the bloodstream as free fatty acids (FFA's), and they are transported
through the blood to the tissues where the energy is needed.
A typical young male adult stores about 60,000 to 100,000 calories of
energy in body fat cells. What triggers the release of all these stored
fatty acids from the fat cell? Simple: When your body needs energy because
you're consuming fewer calories than you are burning (an energy deficit),
then your body releases hormones and enzymes that signal your fat cells
to release your fat reserves instead of keeping them in storage.
For stored fat to be liberated from the fat cell, hydrolysis
(lipolysis or fat breakdown), splits the molecule of triaglycerol into
glycerol and three fatty acids. An important enzyme called hormone
sensitive lipase (HSL) is the catalyst for this reaction. The
stored fat (energy) gets released into the bloodstream as FFA's and they
are shuttled off to the muscles where the energy is needed. As blood
flow increases to the active muscles, more FFA's are delivered to the
muscles that need them.
An important enzyme called lipoprotein lipase (LPL),
then helps the FFA's get inside the mitochondria of the muscle cell,
where the FFA's can be burned for energy. If you've ever taken a biology
class, then you've probably heard of the mitochondria. This is the "cellular
powerhouse" where energy production takes place and this is where
the FFA's go to be burned for energy.
When the FFA's are released from the fat cell, the fat cell shrinks
and that's why you look leaner when you lose body fat - because the fat
cell is now smaller. A small or "empty" fat cell is what you're
after if you want the lean, defined look.
It was once believed that the number of fat cells could not increase
after adulthood, only the size of the fat cells could increase (or decrease).
We now know that fat cells can indeed increase both in size (hypertrophy)
and in number (hyperplasia) and that they are more likely to increase
in number at certain times and under certain circumstances, such as 1)
during late childhood and early puberty, 2) During pregnancy, and 3)
During adulthood when extreme amounts of weight are gained
Some people are genetically predisposed to have more fat cells than
others and women have more fat cells than men. An infant usually has
about 5 - 6 billion fat cells. This number increases during early childhood
and puberty, and a healthy adult with normal body composition has about
25 to 30 billion fat cells. A typical overweight adult has around 75
billion fat cells. But in the case of severe obesity, this number can
be as high as 250 to 300 billion!
The average size (weight) of an adult fat cell is about 0.6 micrograms,
but they can vary in size from 0.2 micograms to 0.9 micrograms. An overweight
person's fat cells can be up to three times larger than a person with
ideal body composition.
Remember, body fat is basically just a reserve source of energy and
fat cells are the like the storage tanks. Unlike a gas tank in your car
which is fixed in size, however, fat cells can expand or shrink in size
depending on how "filled" they are.
Picture a balloon that is not inflated: It's tiny when not filled with
air - maybe the size of your thumb. When you blow it up with air, it
can expand 10 or 12 times it's normal size, because it simply fills up.
That's what happens to fat cells: They start as nearly empty fat storage "tanks" (when
you are lean), and when energy intake exceeds your needs, your fat cells "fill
up" like balloons (not a pretty picture, is it?)
So you don't actually "lose" fat cells, you "shrink" or "empty
out" fat cells. Since fat cells can not only get bigger, but also
multiply, you have be diligent and consistent in your fat-burning lifestyle
because even after you shrink your fat cells, the cells are still there
(in your thighs, lower abs, etc), waiting to be filled up with more fat
again, if you're not careful...
So stay active to keep burning fat and avoid consuming more calories
than you burn, and your fat cells will get shrunk and stay shrunk!
About the Author:
Tom Venuto is a lifetime natural bodybuilder, an NSCA-certified
personal trainer (CPT), certified strength & conditioning specialist
(CSCS), and author of the #1 best-selling e-book, "Burn
the Fat, Feed The Muscle.” Tom has written more than 200
articles and has been featured in print magazines such as IRONMAN,
Australian IRONMAN, Natural Bodybuilding, Muscular Development,
Exercise for Men and Men’s Exercise, as well as on hundreds
of websites worldwide. For information on Tom's Fat Loss program,
visit: www.burnthefat.com
