Binge Eating Affects Dopamine in the Brain

Summary
People who suffer from binge eating disorder feel out of control and eat large amounts of food in a short span of time. The exact molecular mechanism in the brain that causes this disorder is unclear. This study looked at dopamine, a chemical in the brain, in binge and non-binge eaters. Results showed that dopamine secretion in specific parts of the brain increases when binge eaters are presented with food. This rise does not occur in non-binge eaters. The study revealed that this rise in dopamine is not responsible for weight gain and obesity among binge eaters.

Introduction
Binge eating disorder effects 0.7 to 4 percent of people in the U.S. and is prevalent in nearly one-third of obese individuals who are attempting to control their weight. Studies have shown that binge eaters who are also obese tend to eat more than non-binge eaters who are obese. Earlier evidence has revealed that the brain chemical dopamine is involved in motivating food intake. In fact, drugs that diminish dopamine in the brain also diminish appetite. This study was conducted to look into how the brain responds chemically to food, in terms of dopamine release. Both binge eaters and non-binge eaters who are obese were studied in this experiment.

Methodology
* The study examined two groups of participants. The first group consisted of 10 obese people diagnosed with binge eating disorder. The second group consisted of eight obese people who did not have binge eating disorder. All participants were screened for alcohol or drug abuse.
* All participants were given food-related questionnaires that asked them to rate their favorite foods, favorite food-related smells and also foods that decreased appetite. At the end of the questionnaire, they were presented with the top-rated foods.
* While the food was presented to them, their brains were scanned using techniques that measured dopamine release in various parts of the brain. Some of the participants were given a drug (methylphenidate) that causes a rise in dopamine levels of the brain; others were given a placebo.

Results
* On food presentation, all groups (binge eaters as well as non-binge eaters on placebo as well as drugs) felt hunger and desire for food.
* Systolic blood pressure was raised when showed their favorite foods among binge eaters.
* Results showed that when the drug to intensify dopamine release was given along with food stimuli, the brain scans showed increased dopamine. This was significantly higher in binge eaters compared to non-binge eaters.
* Although a dopamine rise was seen in binge eaters, this was not linked to increased body weight of the participant. Thus, dopamine rise could foretell binge eating but not necessarily cause weight gain.

Next steps/Shortcomings
Authors write that the drug methylphenidate that raises brain dopamine levels could have interfered with the response to food presentation. Also, since all participants received the same dose of the drug, those who were heavier or more obese had lower blood concentrations of the drug than others. This could have affected the results. In women participants, the effects of the menstrual cycle and hormonal changes associated with it, were not taken into consideration. This could also have skewed the results since these hormones affect food intake. Also, this was a small, short-term study. Larger studies could reveal more information.

Conclusion
This is the first study that uses brain scans to look at dopamine fluctuations when food is presented to a binge eater. This study is important because obese individuals with a binge eating disorder have more trouble maintaining their weight. They tend to regain weight even after losing it, compared to obese individuals without a binge eating disorder. It provides the information that deeper problems might underlie the condition of obesity and binge eating. Authors suggest that while this study focuses on obese patients with or without binge eating disorder, future studies in non-obese participants could be more enlightening in this regard.

For More Information:
Enhanced Striatal Dopamine Release during Food Stimulation in Binge Eating Disorder
Publication Journal: Obesity, February 2011
By Gene-Jack Wang; Allan Geliebter; Mt. Sinai School of Medicine, New York, New York, and Columbia University, New York, New York

*FYI Living Lab Reports Are Summaries of the Original Research.


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