Addiction: From Drugs to Donuts, Brain Activity May be the Key
I just like food more than you do.
Sound familiar? To some, it’s no more than a shallow excuse for overeating; to others, it’s the only honest way to explain their propensity for consuming bigger portions and eating more frequently.
Whether the claim is a sincere justification or a thinly-veiled excuse, contemporary scientific research has delved into the factors that set those who suffer from obesity and overeating behaviors apart from those who don’t.
While the causes of obesity are not definitively known, scientists have come closer to understanding the differences in neurological processes that separate the eating behaviors of normal-weight subjects from those who have a hard time controlling their eating habits. A particularly significant set of findings shows that obese subjects exhibit qualities of addiction, not unlike those of individuals who engage in substance abuse.
“Today there is a convincing convergence of evidence […] that supports the hypothesis that there are important similarities between overeating highly palatable and hedonic foods and the classic addictions,” wrote the University of Florida’s Dr. Mark S. Gold, who gathered a collection of papers that explored the subject.
Scientists conducting new research have found more pieces of evidence indicating that obese people’s desire to overeat is controlled by the same area of the brain that stimulates drug addicts to crave drugs. While the craving for a ham sandwich may not feel exactly the same as feeling the need to take heroin, scientists have found similar brain conditions that trigger such cravings.
In a test to observe how the brain’s chemistry encouraged overeating by associating positive feelings with consumption, Dr. Gene-Jack Wang and his team of researchers at the U.S. Department of Energy’s Brookhaven National Laboratory studied seven people implanted with a gastric stimulator, a pacemaker-like device that prompts the vagus nerve to expand the stomach, which, in effect, sends a message of fullness to the brain.
When the gastric stimulator was turned on, effectively signaling the brain that the individual was full, scientists noticed substantial changes in metabolism in “brain regions associated with controlling emotions,” Wang said.
The most considerable changes occurred in the area of the brain known as the hippocampus, which is linked to emotional behavior, memory, and the processing of sensory information.
“This provides further evidence of the connection between the hippocampus, the emotions, and the desire to eat,” Wang commented.
Furthermore, tests have shown that these same brain circuits that trigger cravings play a substantial part in consumption behaviors linked to comforting negative emotions. Perhaps this inches closer to scientifically explaining the appeal of a pint of Caramel Double Fudge Marshmallow Butterscotch Whirlwind (the low-fat variety, of course) after your most recent (and, as always, your self-proclaimed final) break-up.
Eat and Be Rewarded
Though it may seem too easy to blame obesity on the onslaught of commercials and ads promoting this powdered sugar-dusted treat and that divinely rich dessert, scientists have uncovered evidence that some people’s brains are at greater risk of falling victim to the simple idea of food.
The research, headed by Andy Calder and Andrew Lawrence of the Medical Research Council’s Cognition and Brain Sciences Unit in Cambridge, revolved around variations in reward sensitivity, a trait that mandates the desire or tendency to pursue experiences that are seen as pleasurable or rewarding. Their research revealed that, for people with higher reward sensitivity, mere pictures of appetizing food caused heightened activity in areas of the brain that deal with motivation and reward.
This information coupled with past research, that the likelihood of becoming overweight is increased in those with higher reward sensitivity and stronger food cravings, has given scientists a better understanding about why certain people are more vulnerable to abnormal, and often unhealthy, eating habits. In essence, people with higher reward sensitivity may simply find more satisfaction in food consumption than others.
“Some peoples’ brain reward centers are more sensitive to appetizing food cues,” said Dr. John Beaver, the lead author of this study. “This helps explain why some individuals are more vulnerable to developing certain disorders like binge-eating.”
Higher reward sensitivity can skew how the brain perceives eating and other pleasurable activities, leading to multiple types of compulsive behaviors and addictions. In these cases, the body may, in fact, take in too much of a good thing, leading to adverse effects on health.
Dopamine: the Key to Unlocking Obesity?
According to another study conducted by researchers at Brookhaven National Laboratory, the brain chemical dopamine – the neurotransmitter associated with triggering feelings of satisfaction and pleasure – may play a significant role in the eating patterns of obese people.
Dopamine is often linked to the pleasure system of the brain. The release of dopamine is brought on by naturally-rewarding experiences and allows the individual to feel enjoyment. Activities like having sex, exercising, eating, and using certain drugs are positively reinforced by the pleasurable feelings that result from the release of dopamine.
As previous studies have pointed to higher levels of dopamine in the brains of people who are addicted to alcohol, cocaine, and other addictive substances, Brookhaven scientists searched for similarities between overeaters and addicts.
“Since eating, like the use of addictive drugs, is a highly reinforcing behavior, inducing feelings of gratification and pleasure, we suspected that obese people might have abnormalities in brain dopamine activity, as well,” said Nora Volkow, a psychiatrist who was involved with the Brookhaven study.
In addition to an increase in dopamine levels, Dr. Gene-Jack Wang and his team of Brookhaven researchers found that overweight subjects had fewer dopamine receptors than normal-weight subjects, coinciding with earlier studies that showed addicts to have less receptors than non-addicts.
According to Dr. Wang, fewer dopamine receptors may cause obese individuals to eat more frequently and consume larger portions of food to reach a point of satisfaction. Though this is a possible explanation for the amount of dopamine and dopamine receptors in obese people, Dr. Wang emphasized that the causal role of dopamine and dopamine receptors was not yet definitive.
“It's possible that obese people have fewer dopamine receptors because their brains are trying to compensate for having chronically high dopamine levels, which are triggered by chronic overeating," said Wang, adding that “it's also possible that these people have low numbers of dopamine receptors to begin with, making them more vulnerable to addictive behaviors including compulsive food intake."
Working Around the Obesity Obstacle
Despite the mounting evidence supporting a direct relationship between brain activity and tendencies toward abnormal eating patterns, Dr. Wong stresses that obesity is a complex disease with a host of factors – genetics, cultural background, and cerebral mechanisms among many others – that contribute to its presence in those who are overweight.
However, the results of these various tests affirm that, when overeating is an addictive behavior, the treatment is similar to rehabilitation from drug use. Pharmacological treatments that are proven to reduce palatability, in conjunction with various behavioral therapies already in use to aid recovering drug addicts, may help people to reverse or avoid unhealthy eating patterns altogether.
While the responsibility of overeating can’t be placed solely on neurological processes, science is proving that it does indeed play a legitimate role. But, until science can turn these findings into a magic solution to eradicate obesity-inducing tendencies, run-of-the-mill willpower may be the one thing you can rely on to put down the pint of Triple Chocolate Mocha Swirl in favor of a couple spoonfuls of low fat lemon sorbet.
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