Why high-protein meat may curb appetite
Brief abstract:
Although levels of fats and sugars have been shown to influence the
desire to eat, until now no team had demonstrated how protein molecules
regulate appetite, the researchers claim. Using rats, researchers looked
at the mTOR enzyme and investigated body response by injections of the
amino acid leucine - found in high protein meats and grains. The leucene
treated animals subsequently ate less and gained less weight. This
appears to substantiate the hypothesis that proteins can curb appetite.

Good news for Atkins? Maybe.

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Why high-protein meat may curb appetite

    * 19:00 11 May 2006
    * NewScientist.com news service
    * Roxanne Khamsi
http://www.newscientist.com/article/dn9147-why-highprotein-meat-may-curb-appetit
e.html

A new appetite-controlling pathway that responds to molecules found in
meat has been discovered in the brain. This brain signal system is
triggered by specific amino acids and may lead to new ways of helping
obese people lose weight, researchers say.

Certain amino acid molecules – the building blocks of proteins – exert
powerful control over appetite, according to a new study in rats.
Animals given injections of the amino acid leucine, which is found in
high-protein meats and grains, gained only about one-third of the weight
put on by their control counterparts.

Although levels of fats and sugars have been shown to influence the
desire to eat, until now no team had demonstrated how protein molecules
regulate appetite, the researchers claim.

Randy Seeley at the University of Cincinnati in Ohio, US, and his
colleagues looked at an enzyme called mTOR, which responds to protein
molecules and regulates their synthesis within cells. They found that
mTOR was highly active in a region of the rat brain called the
hypothalamus – a structure that is involved in regulating appetite in
both humans and rats.

To see whether the mTOR pathway in the hypothalamus responds to amino
acids, Seeley injected 1 microgram of leucine directly into the brains
of rodents, near the hypothalamus. Over the next day, the rats that
received the injection consumed 25 grams of food on average while the
control rats consumed 30 g of food.
Fooled brains

A brief fasting period produced more dramatic results. When the growing
rats were offered food after a 24-hour fasting period, the ones that had
received the leucine brain injections gained just 4 g of weight in a
day. The injection-free controls put on 12 g – three times as much.

Seeley believes the high levels of leucine in the hypothalamus of
injected rats fooled their brains into believing that they had an ample
supply of protein molecules circulating as available fuel in the body.
This tricked their brains into suppressing hunger, he explains.

However, Seeley cautions that the findings do not necessarily explain
why some people claim lose weight on the controversial high-protein
Atkins diet. It remains unclear if ingested leucine has the same effect
as leucine injected directly into the brain, he notes.

Journal reference: Science (DOI: 10.1126/science.1124147)