Hormone may help dieters keep weight off: US study

Reuters

CHICAGO - Falling levels
of a hormone called
leptin that helps the
brain resist tempting
foods may explain why
people who lose
weight often have a
hard time keeping it
off, US researchers
said on Friday.

Restoring leptin to pre-
diet levels may
reverse this problem,
they said, offering a
way for weary dieters
to finally win the
weight battle.

"When you lose weight
you've created about
the perfect storm for
regaining weight," said
Michael Rosenbaum of
Columbia University
Medical Center in New
York, whose research
appears in the Journal
of Clinical
Investigation.

After weight loss
Rosenbaum said the
metabolism not only
becomes more
efficient, so the body
needs fewer calories,
but the brain becomes
more vulnerable to
tasty-looking treats.

"Areas of your brain
involved in telling you
not to eat seem to be
less active. You are
more responsive to
food and you are less
in control of it," he
said in a telephone
interview.

Leptin is a natural
appetite suppressant
secreted by fat cells
in the body. Its
discovery created a
stir in the 1990s when
researchers found
leptin caused mice to
eat less and lose
weight. This rarely
happens in humans.

Since then
researchers have
been looking the best
way to use the
hormone to help treat
obesity.

In earlier studies,
researchers found
that when people lose
weight, leptin levels
fall as the body tries
to protect its energy
stores.

Rosenbaum
investigated the
impact of this loss of
leptin on the brains of
people who had lost
weight, and whether
replacing the hormone
might help them keep
off the weight.

He used an imaging
technique known as
functional magnetic
resonance imaging
that shows activity in
the brain. The
researchers studied
six obese patients
before and after going
on a hospital-
supervised diet that
reduced their body
weight by 10 percent.

People were shown
pictures of food and
non-food items, such
as an apple or a yo-
yo. The researchers
found that after
weight loss, areas in
the brain responsible
for regulating food
intake were less
active when people
were shown food
images. Areas in the
brain responsible for
emotion were more
active.

When the researchers
restored leptin to the
levels before the
dieting, these changes
were largely reversed.

Similar results have
been seen in people
with a rare genetic
condition in which
their bodies do not
make leptin.

Rosenbaum believes
leptin could be a
useful tool in helping
people maintain
weight loss. "The idea
is there should be a
whole new class of
therapies to help us
keep weight off after
we have lost it," he
said.

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