In a way,
weíd all be a little better off if we had more fat,
researchers are discovering.
But before you
reach for the potato chips, know that theyíre talking about
a different kind of fat ó brown fat, which is radically
apart from the white fat that characterizes obesity. In a
sense, theyíre opposites. One burns energy; the other stores
associate professor of cell and development biology at the
University of Pennsylvaniaís Perelman School of Medicine,
studies fats and their relationship to metabolic diseases such
Endocrine Society, an international association focusing on
hormone research, announced that he was one of 13 leading
endocrinologists to get one of its annual Laureate Awards.
Seale received the Richard E. Weitzman Outstanding Early
Career Investigator Award for his study of brown fat.
these issues both as a scientist and as a regular guy. ďI
still struggle all the time with losing weight,Ē he said
during a recent interview about his work. ďMaybe thatís
why Iím fascinated with it. I just find it interesting to
think about how all this works.Ē
different are brown and white fat? Are they really those
very different. Brown fat functions to burn energy, and it
does this to make heat. The heat is really important,
especially in small animals, for maintaining body temperature.
For example, mice that have defective brown fat canít
survive in the cold.
White fat is
the most prevalent fat tissue, especially in humans. Its main
function is to store energy. It expands when people eat more
than they burn off.
are different colors. Brown fat looks brown, and the reason is
it has a lot of mitochondria ó what can be considered the
energy powerhouses of the cell. They essentially make energy
for cells, and brown fat has a lot of them.
The color of
white fat is determined by the lipids that are stored there.
Itís not really that white. In humans, itís more of a
yellow tinge. In mice, itís white.
White fat is
found in the subcutaneous region ó right under your skin and
it surrounds your internal organs. It forms in a lot of
places. Itís far and away the largest type of fat that
Brown fat ó
thereís a lot less of it. And itís in very specific
places. The place itís found in the largest quantities is
right around the collar bone. There are also small amounts
along the spinal column, and quite a bit in the neck. We
donít really know why.
It might be
that the collar bone, spinal column, and neck are just a good
place to be for warming the blood vessels. Brown fat probably
did not form to keep us from becoming obese. It probably
evolved to keep us warm. The heat that it makes can quickly
get to the rest of the body.
Q: So is brown
fat really good for us, while white fat is not?
actually a little more complicated. Theyíre both good.
Brown fat is
good for us because it can burn extra calories; it can expend
calories that you donít want to store. You can kind of think
of it a little like exercise. It will burn energy, except you
donít have to work. This energy would otherwise be stored in
the body, so it actually counteracts obesity in that way.
Itís very clear that mice with more brown fat do very well.
They are protected against obesity and diabetes.
White fat is
also good. The reason is that itís essentially a safe place
to store lipids. Obesity happens when more energy is taken in
than is expended. That energy has to go somewhere. Up until a
certain point, white fat can handle it. The energy is
converted to lipid and stored in white fat. However, if the
oversupply of energy is chronic, the fat cells eventually
become overburdened and arenít able to store the lipid
anymore. It ends up going to liver, pancreas or muscles, and
that causes all kinds of problems.
Q: Can we get
more brown fat by altering what we eat?
A: Not that we
know of. Thereís a lot of interest in that. Large
pharmaceutical companies are trying to figure out how we can
make more brown fat.
The one thing
people can do is to expose yourself to the cold. There are a
lot of people who think that is a good thing to do.
Itís different for each person. Certainly not to the point
where you shiver. There are a lot of studies now looking at
reducing environmental temperature to see if that can have
effects on obesity and diabetes. Itís very promising.
In one Japanese
study, subjects sat in a cold room ó 66 degrees Fahrenheit
ó for two hours a day over the course of six weeks. People
lost quite a bit of weight.
Thereís a lot
of interest in finding other ways to increase the function of
Q: Tell us more
about your research.
A: A lot of
what we are trying to do is to figure out the genetic pathways
for how both brown and white fat cells are made. Weíre
trying to understand the molecules and all the factors that go
into this, with the thought that weíll figure out how to
make more of it or stimulate it in different ways for
The other thing
we focus on is developing animal models so that we can
understand what goes wrong in the setting of obesity and
diabetes ó how that affects fat tissue, both brown and white
ó and how we might be able to change the properties of that
tissue to affect diabetes. When an animal or human gets obese,
that has major effects on the fat tissues. So weíre trying
to understand what is happening ó what is good, what is
potentially bad ó so we can think about ways to intervene.
If we understand the bad consequences, we might be able to
block the effects. If we understand the good consequences, we
might be able to promote them.
We now know a
lot about how these different types of fat tissues work, and
about the genetic factors that control them. Whatís needed
now is to try to find ways to manipulate it, to try to find
therapies that target the fat tissue, for fighting obesity as
well as diabetes. In particular, brown fat holds a lot of
promise for fighting obesity. Itís a tough thing to crack,
but thatís probably where the main thrust of the field is
ó how we can use our knowledge and develop ways to target
brown fat to fight obesity. We have pretty good drugs for
diabetes. Obesity is trickier. And obesity is often the thing
that initiates these other problems.
Q: People tend
to think fat is just bulky, but so much science is revealing
that itís actually more like an organ that does all kinds of
Even in the science community, it was previously thought of as
an inert organ that is a bystander. Now, we know so much more
about it. There are many different types of fat tissue.
Weíve talked about brown and white. In every place in the
body, the fat tissue is probably slightly different and doing
different things, probably having important functions.
The other thing
we know now is that, rather than being an inert organ, it
makes a lot of hormones that communicate with other organs in
the body. It makes things to talk to the brain, that talk to
the muscles. I would say it coordinates or controls a lot of
metabolism. Itís really an important thing to study.