Depriving yourself of sweets - and then bingeing on them - may establish dangerous cycles like those experienced by drug addicts, reports new research.
Withdrawal symptoms as well as physiological changes in the brain can result from a pattern of deprivation and then bingeing, says researcher Carlo Colantuoni, a graduate student at Johns Hopkins University.
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"The bottom line is that the pattern and content of what we eat will really have an impact on the brain and on what we eat in the future," Colantuoni says. "You can get into a dangerous cycle that is self-perpetuating."
Colantuoni and colleagues Bartley Hoebel and Pedro Rada, from Princeton University, based their findings on experiments on rats. Two groups of rats were given access to sugar water and conventional rat food during the nocturnal feeding time, about 12 hours each day. However, one group was denied access to the food for the first four hours of darkness.
After about 30 days of this treatment, those rats not only behaved much differently than the rats that had not been deprived at all, but they also showed significant differences in their brains, Colantuoni says.
Rats that had been deprived of food for the first four hours of darkness ate three times as much sugar water in the first hour after food was delivered as the other group of rats, he says. And, when the food was brought in, they were so excited that they sometimes tore the feeding tubes from the bottles in which the sugar water was stored.
Later, the rats were given naloxone, a drug typically used to treat a heroin overdose. Naloxone blocks particular receptors in the brain and is similar to a drug used to treat eating disorders, Colantuoni says.
When treated with naloxone, the rats that regularly had been deprived of food showed classic signs of drug addiction withdrawal, he says.
"They started to chatter their teeth, as if it was cold: You could see them," Colantuoni says. Other signs of withdrawal appeared, too. "They're more scared, they're less likely to explore new environments [and] their anxiety goes up," he says.
When the rats were killed and their brains examined, the researchers discovered a 30 percent increase in receptors in the nucleus accumbens, an area deep in the brain usually associated with systems of reward. They also found that the rats' dopamine levels had dropped by 50 percent or more. Dopamine, a chemical that transmits messages in the brain, generally is connected with pleasant feelings, experts say. And levels of acetylcholine, linked with unpleasantness, had risen by about the same amount, Colantuoni says.
These physiological changes in the brain track with what's already been seen in the brains of those addicted to cocaine or heroin, he says.
On an evolutionary level, the changes make sense because being deprived of food weakens us, Colantuoni says. Logically, to grow stronger, we need to build up stores of reserves.
But the cycle could prove very harmful to those with eating disorders, who establish the patterns and can't pull out of them, he says, and even people with more minor disorders could have problems. Results of the study were presented this week to the Society for Neuroscience at a meeting in New Orleans.
Dina Zeckhausen, a psychologist who founded the Anti-Eating Disorders League in Atlanta, agrees.
"It fits very well with the experiences of anybody who has tried to go on a diet or certainly anyone with an eating disorder - binge eating or bulimia," Zeckhausen says. Even anorexics, she says, are afraid to start eating because, "intuitively, they know they will not be able to stop," she says.
But the findings also should help in the treatment of people with eating disorders, she says, because they point to a biochemical condition that physically makes it difficult to break the pattern and may help others to not place blame.
"So many of us view it as a weakness in character, a weak will," Zeckhausen says. "We use those words - will power - when in fact it has nothing to do with will but instead a body seeking to not starve itself."
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