Scientists have found evidence that fat and sugar may be addictive,
possibly explaining why many obese people cannot get enough junk food,
despite all the warnings.
Scientists already know that the area of the brain that moderates eating
behaviour is influenced by the blood's level of leptin, a substance
secreted by fat cells.
But a new study by a psychologist at New York's Albert Einstein College of
Medicine has found that rats fed high-fat diets take only three days to
lose their ability to respond to leptin.
"The fatter a person becomes, the more resistant they will be to the
effects of leptin," says Luciano Rossetti in the February 1 issue of New
Scientist.
The magazine reports that another researcher, Sarah Leibowitz, a
neurobiologist at New York's Rockefeller University, found that the level
of galanin, a substance that stimulates eating and curbs the body's use of
energy, increases in the brains of rats that dine on even one fatty meal.
In another experiment rats developed "the shakes" when taken off a
sugar-rich diet, developing symptoms similar to people withdrawing from
nicotine or morphine.
When the rats were given drugs blocking their opiod receptors they
displayed the same neurochemical patterns seen in humans in opiod withdrawal.
"The implication is that some animals - and by extension some people - can
become overly dependent on sweet food," the researcher said.
A University of Wisconsin neuroscientist also reported that rats which
over-indulged showed "long-lasting changes in their brain chemistry similar
to those caused by extended use of morphine or heroin".
But Australian nutritionist Rosemary Stanton was not convinced. "I need
more proof -
all this is based on rats," she
said yesterday, suspecting that eating problems had more to do with habit.
She feared the findings could send the wrong message to the obese. "People
might think there is nothing they can do and will say, 'I might as well go
and have three Big Macs'."
Andrew Byrne, a Sydney doctor who has worked with addicts for 15 years,
warned that addiction was hard to define. However, if the symptoms of
over-eating included being unable to cut down, needing regular consumption,
suffering an adverse reaction, feeling guilty and attracting the attention
of others saying "you are fat", then food was addictive.
Both Ms Stanton and Dr Byrne agreed that if fat and sugar were addictive,
all fast-food ingredients should be listed on packaging.
http://www.smh.com.au/articles/2003/01/30/1043804466415.html
