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01/24/2007
Good Fat, Bad Fat
Last week there were two surprises in our back yard. The first
was when we awoke to find the yard actually covered with snow.
However, I needn’t have bothered to clear the front sidewalk of
the snow since by around noon all of this winter’s first
measurable snow was gone. So far this season it seems that
Malibu has gotten more snow than our part of New Jersey. The
second surprise came when I looked up from reading the Sunday
paper and saw a big red fox that strolled across the yard, jumped
the fence and continued on its way. It was the first fox I’d seen
in decades. Back when I worked at Bell Labs, which borders a
wooded preserve, I did on a couple of occasions see a skinny
grayish fox. Sunday’s fox, however, was definitely on the fat
side and appeared quite well fed.
Speaking of fat, the February issue of Discover magazine has on
its cover a rather startling picture of an obese nude man sitting in
a pose somewhat resembling the sculpture “The Thinker” by
Rodin. The picture relates to an article by Mariana Gosnell titled
“Killer Fat”. I’ve discussed good and bad fats in connection with
diet, most recently in connection with the work at Wake forest
University on monkeys that helped to spur the banning of trans
fats in restaurant foods in New York City. Until I read the article
by Gosnell, I had assumed that fat in the body was all pretty
much the same and that a little fat was OK but too much fat was
a bad thing.
Now I learn that all body fat is not equal and that there are
different types of fat. Not only are there different types of fat but
researchers are also saying that these different body fats don’t
just sit there in your body but actually behave as organs.
Moreover, the different types of fat may even “talk” to each
other or at least sense the presence of each other. To me, fat is
now a whole new ballgame. And, with the health crisis in this
country regarding the epidemic of obesity, it’s a good idea to
become familiar with the good and bad fats in our bodies.
Chances are that you’ve heard it’s more healthful to have a body
shape like a pear rather than like an apple. The apple shape is a
result of fat being concentrated around the middle while in the
pear-shaped individuals the fat is concentrated in the hips, thighs
and buttocks. To minimize the “apple-ness” of your body the
current recommendations are that you women keep your
waistline under 35 inches and you men keep it under 40 inches.
It’s the abdominal region that’s of most concern and here’s
where the two major classes of fat come in.
First, the bad guy – “visceral” fat. Visceral fat resides deep
inside the abdomen and inhabits the space around our vital
organs such as the heart, liver and kidneys. Visceral fat also is
found in the omentum, a flap that hangs off the stomach which is
so thin in a lean person that, if you could poke around inside, you
could see through the flap. In an obese individual, however, the
flap could be inches thick and relatively hard. Excessive visceral
fat has been shown to be a good predictor of all sorts of diseases,
especially in reducing insulin sensitivity, a precursor to diabetes.
Visceral fat has been implicated in heart disease, Alzheimer’s
disease, various cancers and a variety of other maladies.
The other main type of fat is the one you can grab onto and pinch
and may be the most distressing one from the cosmetic
standpoint. This is “peripheral”, or subcutaneous fat. Peripheral
fat lies just under the skin outside the abdominal wall and also is
the type of fat that gravitates to the hips, thighs and buttocks,
where it tends to enhance the probability of having a pear shape.
Peripheral fat is the good fat, even though it may be the kind of
fat you would consider having a liposuction to get rid of it.
Actually, according to the article, it’s peripheral fat that is
removed in a liposuction and there’s some evidence that
removing peripheral fat increases the amount of visceral fat, at
least in some patients. Evidence such as this prompted obesity
specialist Osama Hamdy to say that subcutaneous and visceral
fats are “like two separate organs, each with its own function.
Each senses the other.”
How could fat qualify as an organ of the body? You may recall
that some time ago we talked about leptin, a hormone that
inhibits the appetite. In 1994, it was discovered that leptin is
secreted by fat. Since that initial discovery, a host of other
hormones and biologically active substances have been found to
come from fat cells or cells that reside in fat. Visceral fat is
especially active in churning out large quantities of breakdown
products of fat into the bloodstream. This was thought to be a
possible link with increasing fat being associated with insulin
resistance and diabetes.
However, inflammation has taken center stage more recently. As
one ages and/or becomes more obese, the fat cells get larger and
some rupture. In rupturing they can release chemicals known to
adhere to the walls of blood vessels and also the ruptured cells
attract macrophages to the site to clean up the dead cells. All this
can result in inflammation. The inflammation may just be barely
significant but over a long period of time repeated insults of this
type add up, possibly resulting in insulin resistance and
cardiovascular problems.
How many times do you hear an obese person claim his or her
obesity is genetic? There appears to be a good deal of truth in
that statement. A number of studies of the genes expressed in
human body fats show that peripheral and visceral fats express
certain genes to a greater or lesser extent. Genes have been
identified that appear to influence overall obesity while other
genes seem to be associated with where the fat ends up in one’s
body. For example, James Kirkland of Boston University
Medical Center concludes from his work that how your fat is
distributed is around 70 percent attributable to your genetic
heredity. On the other hand, he blames 50 percent of any
tendency towards overall obesity on genes you inherit from your
ancestors.
What’s the bottom line? Ideally, you’d like to know how much
visceral fat you have but the only way to get a definitive answer
is a CT scan or MRI - not a very realistic option if everyone who
is overweight flooded our tottering medical system to get one.
Central obesity, the fat around your middle as determined with a
tape measure, is a surprisingly good substitute. In 2005, for
example, there was an International Day for the Evaluation of
Abdominal Obesity. On that day over 6,000 primary care
physicians in 63 countries gathered health statistics and waist
measurements of around 180,000 patients. According to Jean-
Pierre Despres, who helped supervise the study, there was a 97
percent correlation in that the greater the waist size the greater
the prevalence of cardiovascular disease and diabetes.
What to do if you’re obese? We all know the answers. Lose
weight, even a modest amount. The bad visceral fat seems to go
first. Exercise, brisk walking for example, also seems to reduce
visceral fat. Don’t eat trans fats – we covered that a few weeks
ago. Question that liposuction – we’ve seen that could increase
visceral fat. Hope for some medical breakthrough in the drug or
other treatment area. Researchers at the Albert Einstein College
of Medicine gave an experimental drug to rats while shining light
on their visceral fat. They lost 40 to 60 percent of that fat!
Another suggested possible treatment I found somewhat weird
was to insert good subcutaneous fat into the visceral fat, hoping
it would somehow counteract the bad stuff.
In the interest of full disclosure, looking at myself in the mirror,
I’m an apple. I just measured my “waist” and was shocked to
find it’s on or an inch or so over the 40-inch mark, depending on
how much I relax. (I put “’waist” in quotes because a kidney
cancer operation over three years ago left me minus a rib and a
resultant bulge that adds at least an inch or two to my girth.) I
think I’m going to speed up my mall walking! Oh, perhaps I
should emphasize that I am not an M.D. and have no medical
expertise other than what I’ve read or have experienced as a
patient.
Allen F. Bortrum
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