Eating And Weight Gain Not Necessarily Linked, Study Shows
ScienceDaily (Jun. 4, 2008) — You may not be what you eat after all. A
new study shows that increased eating does not necessarily lead to
increased fat. The finding in the much-studied roundworm opens the
possibility of identifying new targets for drugs to control weight,
the researchers say.

The discovery reveals that the neurotransmitter serotonin, already
known to control appetite and fat build-up, actually does so through
two separate signaling channels. One set of signals regulates feeding,
and a separate set of signals regulates fat metabolism. The worm,
known scientifically as Caenorhabdtis elegans, shares half of its
genes with humans and is often a predictor of human traits.

The signaling pathways are composed of a series of molecular events
triggered by neurons in the brain that ultimately "instruct" the body
to burn or store fat.

If the "separate-channel" mechanism is also found in humans, weight-
loss drugs might be developed to attack just the fat-deposition
channel rather than the hunger-dampening pathway that has met with
limited success, says Kaveh Ashrafi, PhD, assistant professor of
physiology at UCSF and senior author on the scientific paper reporting
the study.

"It's not that feeding isn't important," Ashrafi says. "But
serotonin's control of fat is distinct from feeding. A weight-loss
strategy that focuses only on eating can only go so far. It may be one
reason why diets fail."

The research is being reported online June 3 by the journal "Cell
Metabolism" and in the print edition June 4.

The finding does not challenge the view that hunger, feeding and fat
are all linked in a feedback loop under the influence of serotonin and
other neurotransmitters that act on neurons in the brain. But the
discovery shows that this is not the whole story, according to
Ashrafi.

Various weight-loss drugs have been developed to boost serotonin and
thereby suppress appetite. But the cutback in eating tends to be short-
term -- often a matter of days, based on animal research, Ashrafi
says. Drugs that block the brain's separate fat-deposition signaling
pathway might be a boon to controlling obesity, type 2 diabetes,
cardiovascular disease and other threats, he adds.

The scientists studied more than 250 genes to identify those that
underlie serotonin's effects on fat and feeding. They found that
serotonin controls feeding by docking with receptors on neurons that
are distinct from those that control fat. In turn, these fat-
controlling neurons send signals to sites of fat storage to rev up
metabolism.

It is widely believed that environments that encourage excessive food
intake and little physical activity promote development of obesity.
However, extensive studies have revealed that body weight is not
merely a passive consequence of environmental conditions but that a
physiological system coordinates the complex mechanisms that regulate
food intake and energy expenditure, Ashrafi says.

This physiological system is thought to involve genes that operate in
various tissues such as fat, muscle, and brain. In fact, the genetic
contribution to body weight is estimated to be between 40 and 70
percent. The molecular mechanisms that link excess fat to various
diseases such as type 2 diabetes are not understood.

To help decipher the complex relationships between behavioral and
metabolic pathways that control body weight, Ashrafi and his team
began analyzing serotonin-induced regulation of fat and feeding in the
microscopic C. elegans worm. They took advantage of a powerful and
relatively new technique known as RNA interference, or RNAi, which
allowed them to inactivate hundreds of genes one at a time to
determine the effect of these gene inactivations on serotonin's
actions on fat regulation.

"Obesity and thinness are not solely determined by feeding behavior,"
the scientists conclude in their paper. "Rather, feeding behavior and
fat metabolism are coordinated but independent responses of the
nervous system to the perception of nutrient availability."

Lead author on the paper is Supriya Srinivasan, PhD, a postdoctoral
fellow in Ashrafi's lab. Co-author at UCSF is Leila Sadegh, BS, staff
research assistant.

Other co-authors are Ida C. Elle, BS, graduate student; Anne G.L.
Christensen, BS, staff research assistant; and Nils J. Faergeman, PhD,
associate professor, all at the University of Southern Denmark.

Research support includes the National Institutes of Health, the
Sandler Opportunity Fund and the Richard and the Susan Smith Family
Foundation Pinnacle Program Project Award.

UCSF is a leading university dedicated to promoting health worldwide
through advanced biomedical research, graduate-level education in the
life sciences and health professions, and excellence in patient care.


----------------------------------------------------------------------------Journal reference:

Srinivasan et al. Serotonin Regulates C. elegans Fat and Feeding
through Independent Molecular Mechanisms. Cell Metabolism, 2008; 7
(6): 533 DOI: 10.1016/j.cmet.2008.04.012
Adapted from materials provided by University of California - San
Francisco.
University of California - San Francisco (2008, June 4). Eating And
Weight Gain Not Necessarily Linked, Study Shows. ScienceDaily.
Retrieved June 5, 2008, from http://www.sciencedaily.com/releases/2008/06/080603121212.htm

On Jun 6, 9:59 am, Lance  wrote:
> Eating And Weight Gain Not Necessarily Linked, Study Shows
> ScienceDaily (Jun. 4, 2008) — You may not be what you eat after all.

Why can't scientist just get the simplest of messages across? Eat less
and you will lose weight. Your metabolism may compensate and weight
loss will stop. Therefore eat even less.

I think being obsessed with diet all the time is a waste of time. And
I tend to gain weight slowly when I'm just eating by instinct, which I
do most of the time. But when I reach the upper range of
'normal' (indicated by belt notch :-) I simply eat less until I go
down a notch. This seems so easy I find it difficult to see why so
many people can't do it. Maybe it's that stupid diet fads &
unnecessary science confuse people, who throw up their hands in
disgust, and don't think about it again.

Publishers note, I'm open to offers to produce a best seller on my
diet technique, which never fails. "Eat less and get slim" :-)

On Jun 8, 10:59 am, Paul Grieg  wrote:
> On Jun 6, 9:59 am, Lance  wrote:
>
> > Eating And Weight Gain Not Necessarily Linked, Study Shows
> > ScienceDaily (Jun. 4, 2008) — You may not be what you eat after all.
>
> Why can't scientist just get the simplest of messages across? Eat less
> and you will lose weight. Your metabolism may compensate and weight
> loss will stop. Therefore eat even less.
>
> I think being obsessed with diet all the time is a waste of time. And
> I tend to gain weight slowly when I'm just eating by instinct, which I
> do most of the time. But when I reach the upper range of
> 'normal' (indicated by belt notch :-) I simply eat less until I go
> down a notch. This seems so easy I find it difficult to see why so
> many people can't do it. Maybe it's that stupid diet fads &
> unnecessary science confuse people, who throw up their hands in
> disgust, and don't think about it again.
>
> Publishers note, I'm open to offers to produce a best seller on my
> diet technique, which never fails. "Eat less and get slim" :-)

You really should offer your services as a health professional.
Perhaps Oprah will interview you. Your insights are startling!

Lance