|
||||||
|
|
|
|
|||||||||||
|
|||||||||||||
| ||||||||||||||||||||||||||||||||||||
Obese individuals show addictive qualities similar to those of substanceabusers, suggesting that substance abuse treatments may also be effectivetreatments for obesity, according to a special series of papers on thesubject, in the July 2004 issue of the Journal of AddictiveDiseases.
"Today there is a convincing convergence of evidence from the benchin neuroscience, to PET [positron emission tomography] and fMRI [functionalmagnetic resonance imaging] neuroimaging, to data from clinical experiencethat support the hypothesis that there are important similarities betweenovereating highly palatable and hedonic foods and the classicaddictions," writes Mark S. Gold, MD, of the University of Florida,Gainesville, in his introduction to the collection of research papers.
Researchers understood from earlier studies that overfed animals willinglylimit their self-administration of drugs and, conversely, starved animalsincrease such self-administration. Findings from more recent brain imagingstudies in people exposed similar neural activity patterns in response tosubstance use and overeating.
One such study was conducted by Gene-Jack Wang, MD, and colleagues atBrookhaven National Laboratory in Upton, N.Y. The researchers found the braincircuits of obese individuals, when compared with people of normal weight,have fewer receptors for dopamine, the neurotransmitter associated withfeelings of satisfaction and pleasure. Fewer dopamine receptors may driveobese individuals to need more food more frequently to obtain satisfaction.Similar research conducted in substance abusers revealed they also have fewdopaminereceptors.1
BRAIN FUNCTION STUDIES
Wang and colleagues also found that obese individuals have higher metabolicactivity than normal weight individuals in the brain regions associated withsensory input from the mouth, lips, and tongue. This suggests obeseindividuals experience a higher level of satisfaction from eating than peopleof normal weight.
Gold and colleagues G. Andrew James, PhD, and Yijun Liu, PhD, also at theUniversity of Florida, report that fMRI studies show significantly differentresponses to glucose ingestion in obese people than in people of normalweight. These responses permit obese individuals to eat for a longer durationbefore their brain responds with signals of satiety, according toinvestigators.2
Research also indicates that the brain area assigned to the mouth andeating in obese individuals is larger than in people of normal weight, Goldtold DOC News. Weight loss becomes more difficult as weight increasesin obese individuals, he explains, due to the combined effect of a moreintense sensory perception for the mouth, lips, and tongue, and the delayedbrain response to food signals.
Eating is a highly reinforcing behavior that can elicit powerfulconditioned responses, Wang observes. In yet another study, published in theApril 2004 issue of NeuroImage, he and colleagues assessed wholebrain metabolism in food-deprived volunteers of normalweight.3 PETrevealed that food stimuli caused a significant increase in whole-brainmetabolism, as well as in the volunteers' reports of hunger and desire forfood, while nonfood stimuli did not.
COMPETING CRAVINGS
Satiety from food and alcohol ingestion may compete for the same rewardsites in the human brain, according to investigators. Researchers assessedalcohol consumption as part of a prebariatric evaluation in a group of nearly300 female patients with body mass index (BMI) ranging from 27 to 107. Morethan 62% of those categorized as overweight—BMI from 27 to29—reported alcohol use in the past year. However in the remainingpatients, the researchers found that alcohol consumption decreased as BMIincreased. Alcohol use decreased to less than 48% among patients with BMI from30 to 39, to less than 42% among those with BMI of 40–49, and to justover 35% among those with BMI of 50 orgreater.4
It is commonly observed in weight management and bariatric surgery clinics,Gold notes, that the heavier the patient, the less alcohol and illegal drugshe or she uses. Additionally, he remarks, treatment for smoking cessationcauses weight gain as does "all supervised drug abstinencetreatment."
When combined, this evidence implies that chronic overeating is associatedwith addictive qualities and suggests that treatments used for substance abuseaddictions, such as behavior therapies and pharmacological interventions thataffect the body's response to specific substances, may also effectively treatovereating and obesity.
BMI AS A VITAL SIGN
Gold believes the first step in treating overeating is for generalpractitioners to consider BMI a vital sign. A BMI of 27 or higher shouldtrigger clinicians to conduct motivational interviews and evaluations of theirpatients.
Once individual evaluations and motivational assessments indicate thepatient's openness to treatment, clinicians can oversee therapies that bestmeet the patient's needs. Patients may need guidance in setting realisticgoals that include diet and exercise targets. Primary care providers mayconsider "strategies that utilize motivation, group support, medicationto treat concurrent disorders, and medication for the disease ofobesity," says Gold. Also, some patients are candidates for surgicaltreatment, and general practitioners can help identify and refer such patientsto specialists.
Current pharmaceutical obesity treatments include sibutramine (an oralappetite suppressant that appears to increase the activity of norepinephrineand serotonin in the brain) and orlistat (an oral lipase inhibitor thatprevents intestinal absorption of some fats). Each medication carries specificcontraindications and side effects and both medications require patients toconcurrently follow low-calorie diets.
Gold suggests enlisting the support of family and friends to help motivatepatients in their efforts to lose weight, adding that obesity is a"chronic, medical, relapsing illness that requires a highly motivatedperson and a strong support system for success." Family and friends maybe especially useful with patients not motivated to lose weight "bypersonalizing what the illness means to them and the fears that they haveabout the patient's health and function," he says.
"Redefining obesity as the product of a substance dependence disorderwould alleviate the stigma associated with this illness," according toGold and colleagues. Redefining obesity as a substance dependence may alsoprovide "new directions for treating this growing epidemic."
References
2. James GA, Gold MS, Liu Y: Interaction of satiety and rewardresponse to food stimulation. J Addict Dis 23: 23–37, 2004.[Medline]
3. Wang GJ, Volkow ND, Telang F, et al.: Exposure to appetitive foodstimuli markedly activates the human brain. NeuroImage 21: 1790–1797, 2004.[Medline]
4. Kleiner KD, Gold MS, Frost-Pineda K, Lenz-Brunsman B, Perri MG,Jacobs WS: Body mass index and alcohol use. J AddictDis 23:105–118, 2004.[Medline]
CiteULike 
Del.icio.us 
Digg 
Reddit 
Technorati What's this?
| ||||||||||||||||||||||||||||||||||||
|
||||||
|
| DOC News | Diabetes | Diabetes Care | Clinical Diabetes | Diabetes Spectrum |
