For many years, the conventional wisdom about fat
was that it was essentially just the body's fuel
storage facility: inert, convenient and pretty cute on
But too much of it on grownups, and we tend not to
think it's so cute. And now recent research has
shown that it's not so inert, either. Your body's fat
isn't just passively storing energy until you need it. It
turns out there are other things going on in there,
sinister things that could be causing you health
Everybody knows that excessive weight aggravates,
even causes, many unhealthy medical conditions,
including bone and joint disorders, cardiovascular
disease, pulmonary problems and diabetes.
Fat's role in some of these problems has often been
attributed to what might be called the physical
effects of the excess weight: the wearing burden of
weight on bones and joints, the buildup of plaque
that reduces blood flow through major arteries, the
crowding of fat around critical body organs, causing
strain on those systems.
But it's the role fat plays at the chemical level that is
of growing interest today, because one of the most
important revelations to come from these recent
studies that fat is actually producing chemicals that
cause inflammation, a key player in all those
troublesome and dangerous diseases.
Weight problems are typically regarded as issues of
the metabolic system, while inflammation has been
seen as a function of the immune system. In its
normal role, inflammation is a protective device,
defending the body against outside invaders. But it
becomes an unhealthy condition when it reacts
excessively, or in extreme cases, mistakenly attacks
healthy tissues, as with rheumatoid arthritis.
The metabolic and immune systems actually are
bound together. That's created certain problems
through most of human history, because when people
are malnourished or starving--which remains a
problem in undeveloped portions of the world--their
metabolism slows down, trying to conserve every bit
of energy it can. And this in turn suppresses the
immune system which is then less able to fight off
But here in the United States, we're facing a problem
at the other end of the scale. With roughly two
thirds of the population now overweight, a different
set of complications and problems has emerged from
the immune/metabolic relationship, the most
prominent of which is excess inflammation.
That's because fatty tissue is made up of adipose
cells, which increase in size but not number as more
fuel is presented to the body for storage. These cells
produce something called cytokines, small, secreted
proteins that among other things, produce and
regulate immunities and inflammation. And as adipose
cells grow larger, they produce more cytokines,
leading to more inflammation.
Not only that, but in amongst the fatty adipose cells
are other cells called macrophages, which also
produce cytokines. There are normally a few
macrophages in the fatty tissue of even slim people,
but as people become heavier, gradually at first and
then at an increasing rate, the proportion of
macrophages in fatty tissue increases.
Now, you wouldn't want to be without macrophages--
these are the immune system's first line of defense,
patrolling the body for infection and cleaning up after
cells as they naturally die off. So you want--
actually, need--a normal number of these little guys
distributed throughout your tissues.
But it turns out that in overweight people, most of
the inflammation promoting cytokines in fat are
coming not from the adipose cells themselves, but
from these macrophages!
The clean-up crew
So what is it that attracts the extra macrophages,
with their dangerous cargo of inflammatory
cytokines, into the fatty tissue to begin with'
Recall that as people become increasingly
overweight, they do not grow more adipose cells; the
ones they have simply swell to larger and larger size.
Inevitably, some of them become so overburdened
that they burst open, leak, or just die. It is the
resultant mess of cellular waste that the
macrophages come rushing in to clean up, after all,
that's their job!
But with that clean-up mission, you get all that
excess inflammation that they bring, and you know
what that means: more heart disease, more arthritis,
more diabetes, more asthma.
But wait! You may say, that's great! That means we
can just surgically remove some of our fat--and all
its macrophages with it--- and thereby reduce our
risk of those diseases!
As usual, there's no easy way out of the health
problems caused by excess weight. Liposuction can't
bail us out of inflammatory heart disease or arthritis.
That's because not all fat is created equal.
Visceral fat that's packed in around the organs in our
abdominal cavity---where no cosmetic surgeon can
vacuum it away--that's the stuff that's packing all
the inflammatory activity, whereas the subcutaneous
body fat hanging around our hips and arms, not so
When people underwent fat-reduction surgery for
cosmetic purposes, a process that removes primarily
that subcutaneous body fat, they had no
improvement in their inflammation measures at all.
But in another study, when only visceral fat was
removed from a group of extremely obese men who
had insulin resistance, by one year after surgery,
95.6% of the men no longer had insulin resistance.
They still had all their excess body fat, but the most
of the inflammatory cytokines associated with insulin
resistance had been taken out of commission.
Obviously, that's extremely dangerous surgery, and
very heavy people are exceptionally high-risk
candidates for major surgery anyway, so there's no
quick fix there.
But the same old good news as always remains:
weight loss through diet and exercise will improve the
situation. Several studies have confirmed that as
overweight people lose weight through those simple--
-though not necessarily easy--lifestyle changes,
those inflammation-producing cytokines are reduced
and numerous health measures improve.
Finding the inflammatory properties of fat is one of
those discoveries that doesn't readily offer any easy
solutions, but it sure helps explain why excess weight
causes so very many problems.