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4 June 2008
You Aren't What You Eat 
A fascinating new study shows that increased eating does not necessarily lead to increased fat, opening the possibility of new drugs to control weight, researchers from the University of California - San Francisco say. Explaining their findings in the journal Cell Metabolism, the researchers said their 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 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 can be exploited, 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, said the study's senior author Kaveh Ashrafi. "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 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. "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." Related:
Sacre Bleu! Americans Are Dumb Eaters
How Low-Carb Diets Suppress Hunger
More Evidence For Obesity Virus
Study Slams Effectiveness Of Dieting Source: University of California - San Francisco
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