7th MAY 2020 - Page 21



Wednesday, March 7, 2018
www.irishnews.com
35
Scientists say ‘Switching on’ calorie-burning fatcells you’ve had since birth
means that you can slim – without trying. So what’s the secret?
By Jerome Burne
F
OR the dieter, it sounds
like the dream solution: a
type of fat cell that burns
fat, rather than storing it
— and all you need is just
85g (3 oz) of these cells on
your body to burn an additional 400
to 500 calories every day.
That’s approximately the daily
calorie reduction you might get on a
regular weight-loss diet. But, unlike
such a diet, you wouldn’t need to
cut your calorie intake or do extra
exercise.
These ‘magic’ fat cells are known
as brown fat. We’ve known about
them for a while, but the drawback,
scientists used to believe, was that
only a small percentage of us have
brown fat.
Babies have it, but it disappears
as we grow up, leaving us with
just small deposits above the
collarbones and at the top of the
spine. And it was thought that,
as an adult, the only sure way
to boost your brown cell count
was to regularly make yourself
uncomfortably cold for hours at a
time.
Now, however, our understanding
of it has changed. Not only are
many more of us likely to have
brown fat — and three times more
of it than we thought — but recent
research has found a much more
palatable way to activate it: by
eating a carbohydrate-rich meal.
Specifically, in the case of the
study that discovered this, eat:
vegetable lasagne, milk, rye bread
and blueberry soup.
Brown fat was first spotted in lab
rats at St George’s Hospital Medical
School, London, 40 years ago. The
theory is that it first appeared in
small mammals in the days of the
dinosaurs, allowing them to escape
giant predators by moving into the
cold north.
Modern research is now full of
reports of hardy human volunteers
spending hours a week shivering
in freezing rooms to activate their
brown fat.
It’s not a strategy that’s about to
go mainstream any time soon. This
has encouraged labs and drugs
firms to spend millions of pounds
in a quest to discover the pill that
would make your brown fat cells
more efficient and stimulate your
body to create more.
But now, a team at the Technical
University of Munich (TUM), in
Germany, look as if they have hit
the jackpot. They’ve found a way of
waking up your brown fat cells that
uses the same pathways in your
body that respond in a refrigerated
room, but which is a lot more
pleasant: having a carbohydraterich meal.
The 25 volunteers in the study,
published in the journal Cell
Metabolism, ate a 500-calorie meal
made up of 58 per cent carbs that
included vegetable lasagne, milk,
rye bread and blueberry soup.
‘These are all foods commonly
eaten in Finland,’ said Kirsi
Virtanen, a professor of clinical
nutrition at the University of
Boosting your levels
of ‘baby fat’ can help
you lose weight
Eastern Finland,
who was part
of the research
team. ‘You may
not regard
lasagne as a
typical Finnish
food but,
nowadays, pasta
is widely eaten here
and blueberry soup is a
popular dessert. The pasta
and the bread were the main
sources of carbohydrates.’
The researchers estimated that
brown fat burned an average of 28
calories for every 100g of food they
ate. An admittedly modest figure,
but the scientists calculated that,
at that rate, a hundred or so grams
of brown fat could burn off the
equivalent of 25,000 calories a year,
which would otherwise have been
stored as 3.4kg of white fat.
‘For the first time, we
demonstrated that heat generation
in brown adipose [fat] tissue
could be activated by a test
meal just as it would by
exposure to cold,’ said
the lead researcher,
Professor Martin
Klingenspor.
The finding that a
carb-rich meal can
stimulate fat-burning seems
surprising, as the extra sugar (or
glucose) when the meal was broken
down would normally be swept into
fat stores.
But the team found the meal’s
effect of raising insulin levels (the
body produces insulin to mop up
sugar from the blood) turned on the
brown fat cells as cold does.
‘We have clinical experience of
obese patients who are able to
balance their metabolism and lose
weight by just eating regularly and
controlling the size of the meal,’
says Professor Virtanen.
They also found insulin made the
now-activated brown cells take in
more glucose to burn off.
The challenge now is to find the
sweet spot between the insulin
level that allows extra glucose to
be burnt off and the level at which
insulin stores it in the white fat
cells. In other positive news, results
of an earlier study by the same
We have clinical experience of
obese patients who are able to
balance their metabolism and lose
weight by just eating regularly and
controlling the size of the meal.
Professor Virtanen
team suggest we actually have
three times more brown fat on our
bodies than used to be thought —
meaning that there is potentially
more to activate.
Brown fat is detectable with the
PET scans used to spot growing
tumours in cancer patients: cancer
cells absorb far more glucose
than healthy cells. Brown fat
cells also use up far more
glucose than regular
white fat cells.
The new areas where
the extra brown fat
showed up included
around the heart, in
the space between the
breast bone and the
spine and above the
kidneys.
Professor
Klingenspor and his
team analysed more
than 1,600 existing PET
scans and found more brown
fat than expected. They also
observed various other features:
that women’s deposits were more
active than men’s and that the
thinner and younger you are, the
more you have.
‘When you put these
results together
with other recent
findings, it’s clear
there is much
greater scope for
manipulating both
white and brown fat
cells than we used to
think,’ says Dr Benjamin
Bikman, an assistant professor
of pathophysiology specialising
in diabetes at Brigham Young
University in Utah, in the U.S., and a
leading expert.
None of these findings, however,
has led to a new weight-loss drug
treatment, due mostly to sideeffects. One of the first studies to
show cells can be changed found
that the hormone irisin, made by
the muscles in exercise, caused
the white cells to behave more like
brown ones — however, looking for
a drug that can repliacte the effects
of exercise has proved elusive: a
growth factor called FGF21 did the
same thing, but it also raised the
risk of fragile bones.
A protein called PPAR-y also
encouraged new brown fat cells to
grow, but it was linked with weight
gain and heart disease.
A hormone called orexin that
controls how awake you feel, as well
as appetite, also activates brown
cells, but the drug company that
developed it has had it licensed
as a treatment for narcolepsy and
insomnia and has not explored its
weight-loss potential.
C
uriously, the hormone
insulin, known to be
involved in obesity and
diabetes, hasn’t played
much part in brown fat research
so far. In apparent contrast to the
latest findings, Dr Bikman’s work
has found that for brown fat cells
to be active, insulin levels must be
low. He says: ‘Once you get high
levels of insulin, which come with
diabetes and regularly eating a highcarbohydrate diet, brown fat cell
activity drops right down.’
Giving extra insulin to rats and
mice in the laboratory makes brown
fat cells store glucose instead of
burning it.
Brown fat has been a puzzle since
it was first spotted and these latest
findings create new ones.
Too much insulin turns it off, but,
without some insulin, it won’t be
turned on at all.
A carbohydrate-based diet that
© Solo dmg media
Not all fat cells are bad news
T
HOUGHT all fat was the
same? here, we look at the
three types lurking under
your skin . . .
White fat: This is the familiar,
yellow-ish fat that you put on if
you eat too many calories — the
stuff you can pinch. As well as
storing energy, white fat acts
as an insulator and cushion for
your organs. Excess white fat
around the abdominal organs
(known as visceral fat) is linked
to health problems including
type 2 diabetes, heart attacks and
cancer.
Brown fat: It’s called ‘brown’,
but the shade can range from
dark red to tan (the colour comes
from its higher concentrations
of iron). While white fat stores
excess energy, brown fat burns
it to generate heat and maintain
the body’s core temperature.
Scientists are now looking at
ways to ‘switch on’ or even
expand our brown fat stores —
it’s known that exposure to cold
in some people spurs their brown
fat into action.
Beige fat: This is a newly
discovered form of fat that
burns calories, although not as
effectively as brown fat. It occurs
as a result of cold or exercise,
which appear temporarily to turn
white fat into beige — which
could help explain the so-called
‘afterburn’ (higher use) of calories
experienced following a workout.
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