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[IP] Study suggests why its so hard for us to resist junk food


Just the sight of food lights up brain

Study suggests why its so hard for us to resist junk food

By Maggie Fox

May 22  The very sight of food causes the brain to react with pleasure, 
scientists said on Wednesday in a report they say shows why so many people 
cant resist temptation when it comes to food.

    THE REACTION looks very different from the way the brain lights up when 
people actually eat  and explains the phenomenal success of advertisements 
for junk food and snacks, the team at the U.S. Department of Energys 
Brookhaven National Laboratory found.
       This shows us why all the advertisements about food are so powerful 
and why we are having problems with obesity in this country  because we are 
constantly being bombarded with food stimuli, said Dr. Nora Volkow, a 
psychiatrist who led the study.
       The good news is that if people are aware of what is going on they 
may be able consciously to block the effects of advertising, the smell of 
bread in the supermarket and other stimuli that make people want to eat when 
they know they should not.

       Volkow and colleagues used positron emission tomography (PET) brain 
scans to measure dopamine levels in 10 hungry volunteers. Dopamine is a key 
neurotransmitter, or message-carrying chemical, associated with pleasure.
       They were all of normal weight, Volkow said. We asked them what 
their favorite foods were. Then first we studied them under a condition 
where there was no stimulation of food  we just asked them to please tell 
us about their family genealogy.

       While this was going on, each volunteer underwent a PET scan. Writing 
in the June 1 issue of the journal Synapse, Volkow and colleagues said this 
gave them a baseline measurement for the next step.
       Then we exposed them to the food they said they liked. But we told 
them they wouldnt be able to eat it, she said. We were being a little 
mean for the good of science.
       The dopamine levels shot up, she said.
       This is perfectly normal, Volkow added.
       It is obviously a mechanism by which nature ensures that we actually 
consume food when food is available, she said.
       We never know when food is going to be available. Well, now we do 
because we have (convenience stores). But when we were evolving we didnt, 
and when there was food accessible you had to eat it.
       The system worked well for millennia.

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