Science is verifying what many overeaters have suspected for a long time: sugar can be addictive.
In fact, the sweetener seems to prompt the same chemical changes in the brain seen in people who abuse drugs such as cocaine and heroin.
"Our evidence from an animal model suggests that bingeing on sugar can act in the brain in ways very similar to drugs of abuse," lead researcher Bart Hoebel, a professor of psychology at Princeton University, said.
Behavioural and neuro-chemical changes
"Drinking large amounts of sugar water when hungry can cause behavioural changes and even neuro-chemical changes in the brain which resemble changes that are produced when animals or people take substances of abuse. These animals show signs of withdrawal and even long-lasting effects that might resemble craving," he said.
Dr Louis Aronne, director of the Comprehensive Weight Control Program at New York-Presbyterian Hospital/Weill Cornell Medical Centre in New York City, added: "The big question has been whether it's just a behavioural thing or is it a metabolic chemical thing, and evidence like this supports the idea that something chemical is going on."
A "sugar addiction" may even act as a "gateway" to later abuse of drugs such as alcohol, Hoebel said.
Sugar addicts suffer withdrawl
The stages of addiction, as defined by the American Psychiatric Association, include bingeing, withdrawal and craving.
For the new research, rats were denied food for 12 hours a day, then were given access to food and sugar (25% glucose and 10% sucrose, similar to a soft drink) for 12 hours a day, for three to four weeks.
The bingeing released a surge of the neurotransmitter dopamine each time in the part of the brain involved in reward, the nucleus accumbens. "It's been known that drugs of abuse release or increase the levels of dopamine in that part of the brain," Hoebel said.
But it wasn't only the sugar that caused this effect, Hoebel explained - it was the sugar combined with the alternating schedule of deprivation and largesse. After three weeks, the rats showed signs of withdrawal similar to those seen when people stop smoking or drinking alcohol or using morphine.
Anxiety, depression followed
The scientists next blocked the animals' brain endorphins and found withdrawal symptoms, anxiety, behavioural depression and a drop in dopamine levels. In other words, they confirmed a neuro-chemical link with the rats' behaviour.
But longer periods of abstinence didn't "cure" the rats. Instead, there were long-lasting effects with the animals: They ingested more sugar than before, as if they were craving the substance and, without sugar, they drank more alcohol.
The researchers speculated that some of these brain changes may also occur in people with eating disorders such as bulimia and anorexia, although more research needs to be done to confirm the effects in humans.
"Some say it's easy to lose weight - you just have to shut your mouth, stop eating so much," Aronne said. "I tell them a good way to overcome global warming is if people made less carbon dioxide by breathing less. Obviously, that's absurd. You can't do it because you feel uncomfortable.
"The same thing is true of eating," he added. "Fattening food has an impact on the regulating mechanism that breaks down your sense of fullness, makes you feel an urge to go back and get that blast of sugar and this creates the vicious cycle of weight gain that we're going through." - (Amanda Gardner/HealthDay News)