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Addiction In Dieters
Dieters Can Experience Neurobiological Similarities Of Drug Addicts
Researchers from Boston University School of Medicine (BUSM) have
shown that intermittent access to foods rich in fat and sugar induces
changes in the brain which are comparable to those observed in drug
dependence. The findings, reported in the journal Proceedings of the
National Academy of Sciences, may explain how abstinence from these
foods contributes to relapse eating among dieters as well as related
Forms of obesity and eating disorders can be defined as chronic
relapsing conditions with alternating periods of abstinence (dieting
to avoid "forbidden" foods-rich in sugar and fat also known as
palatable foods) and relapse (compulsive, often uncontrollable, eating
of highly-palatable foods) that continue despite negative
consequences. Although the positive reinforcing properties of
palatable foods are well known, less attention has been given to the
increased probability of a behavioral response produced by removal of
an aversive stimulus (intake of palatable food to relieve negative
The researchers used 155 rats to measure the neurobiological
responses. The first group, the diet cycled subjects, repeatedly ate
standard rat chow for five days, followed by a highly palatable, high-
sugar, chocolate-flavored chow for two days. The second group ate only
standard food. The amount of food consumed was not restricted for
either group. When the diet-cycled rats were fed standard chow, they
showed less motivation to obtain it, refused it, although it was
previously acceptable, and they exhibited anxiety. However when the
rats resumed eating the palatable food, they overate and their anxiety-
related behaviors returned to normal.
The researchers then looked at the role of the brain's stress system,
which contributes to cycles of drug and alcohol binging and
withdrawal, in driving these behaviors. They found that during
abstinence from palatable foods, the rats showed increased
corticotropin-releasing factor (CRF) gene expression and peptide in
the amygdala, an area of the brain involved in fear, anxiety and
stress responses. Similar to the anxiety, only when the diet-cycled
group was fed palatable food did CRF levels return to normal.
Importantly, the blockade of the CRF receptor 1 with a selective
antagonist was able to prevent all the behavioral outcomes of
palatable food withdrawal.
According to the researchers, CRF is a key stress neurotransmitter.
"In observing the activation of the amygdaloid CRF system during
abstinence from palatable foods, we understood the causes of recurrent
dieting failures," said study co-author Pietro Cottone, PhD, an
assistant professor and co-director of the Laboratory of Addictive
Disorders in the Department of Pharmacology and Experimental
Therapeutics at BUSM.
"CRF activation during abstinence from palatable foods induces a
negative emotional state which is responsible for signs of anxiety and
contributes to relapse to 'forbidden foods,'" added study co-author
Valentina Sabino, PhD, an assistant professor and co-Director of the
Laboratory of Addictive Disorders in the Department of Pharmacology
and Experimental Therapeutics at BUSM. "The stress experienced by
frequent dieters in abstinence from palatable food has neurobiological
similarities to the negative emotional state of drug and alcohol
In addition to Cottone and Sabino, the paper, "CRF system recruitment
mediates dark side of compulsive eating," was authored by Marisa
Roberto, Michal Bajo, Lara Pockros, Jennifer B. Frihauf, Eva M.
Fekete, Bruno Conti, George Koob and Eric Zorrilla from the Scripps
Research Insitutute; Luca Steardo of the University of Roma La
Sapienza (Rome, Italy); Kenner C. Rice of the National Institute on
Drug Abuse of the National Institutes of Health (NIH), and Dimitri E.
Grigoriadis of Neurocrine Biosciences.
This study was supported by the National Institute on Drug Abuse; the
National Institute on Alcohol Abuse and Alcoholism; the National
Institute of Diabetes and Digestive and Kidney Diseases; the Pearson
Center for Alcoholism and Addiction Research; the Intramural Research
Programs of the National Institute on Drug Abuse and the National
Institute on Alcohol Abuse and Alcoholism.
Source: Michelle Roberts
Boston University Medical Center
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