Addictive behaviors present a challenge, since it is problematic for an observer to understand why clearly harmful behaviors are continued. However, we frequently see used alcoholics who drink despite liver damage or social consequences, smokers who smoke despite lung or heart damage, and morbidly obese patients who continue steadily to overeat despite the resulting health threats and compromised function. Lately, we’ve learned a good deal concerning the reinforcing ramifications of addictive substances on the brain. Neurochemical pathways involving such potent neurotransmitters as dopamine, serotonin, gamma-aminobutyric acid, and glutamate are influenced by exposure to many substances with the potential for addiction or abuse. Repeated contact with these addicting substances results in stimulation and modulation of reward pathways that, subsequently, make such substances more attractive and harder to resist. There is some evidence from neuroimaging that, despite years of abstinence, these pathways may never return for their preaddiction state, raising the chance of relapse with reexposure. Overeating clearly shares factors with other addictive behaviors. The overeater persists even in the face area of negative physical consequences and societal disapproval, includes a high frequency of relapse, and clearly finds rewards in the behavior that are not readily apparent to the observer and that override the most obvious negative consequences. Recent studies in human and animal subjects claim that a number of the same neurotransmitter systems active in addiction might be active in the persistence of harmful eating behaviors. Nora Volkow, among the nation’s premier researchers on addictive behaviors, has proposed a standard model for both obesity and drug abuse and addiction, with dopamine pathways in the mind playing a vital role. In every addictive behaviors, she hypothesizes that the addicted individual assigns an enhanced salience or meaning to a specific reinforcer (drugs or food) at the cost of other reinforcers.
This is due to conditioned learning and resetting of the brain’s reward thresholds by repeated stimulation either by substances of abuse or by large quantities of palatable food, usually nutrientdense sugars or fats. In this model, contact with the food or drug reinforcer or conditioned cues for consumption triggers the dopamine-modulated neuronal reward and motivation circuits, while inhibiting cognitive control.5 Thus, the drive to consume is stimulated, and the ability to inhibit the drive is diminished, a challenging combination to overcome despite the very best of intentions. In a study considering gender differences in brain reaction to food stimulation, Volkow and her colleagues6 found male subjects had a better power to inhibit brain activation in a reaction to food stimulation in multiple regions, such as the amygdala, hippocampus, insula, orbitofrontal cortex, and striatum. Volkow et al hypothesized this difference in ability to dampen a reaction to food stimulation can lead to a lowered ability to suppress hunger in women and the resulting gender difference in obesity. Alternation of access and restriction may enhance the addictive eating pattern, resulting in the familiar cycle of successful dieting followed by a rebound to the pre-diet weight as well as higher.7 Imaging studies of obese and lean individuals who’re anticipating calorie-rich tasty food versus a tasteless solution demonstrate that obese subjects respond with greater activity in the gustatory and somatosensory parts of the mind and decreased activation in the striatum. This decreased activity may reflect a genetically mediated reduction in dopamine signaling because region, leading these individuals to overeat to compensate for the hypofunctional dorsal striatum.8,9 The continued growth of obesity inside our society regardless of the proliferation of “lite” and “low-fat” foods emphasizes that there’s no shortcut to healthy eating, and a recently available commentary in the Journal of the American Medical Association highlights that even efforts to curb calorie intake through the usage of artificial sweeteners may not trump neurobiology. Mcdougal cites an observational study that found a dose–response relationship between usage of diet drinks and measurement of adiposity as time passes, in addition to studies finding daily consumption of such drinks associated with metabolic syndrome and risk of diabetes, although the direction of the causality was not clear. A lot more concerning, studies with experimental animals found the drive for sweetness led them to select saccharine over intravenous cocaine, previously considered to be one of the very most addictive substances. The risk for the human would-be dieter is that the use of these hyper-sweet sugar substitutes may overstimulate sweetness receptors, causing them to revert to an infantile state and making a healthy diet of energy-dilute foods less palatable.10 David Kessler,11 the former chief of the Food and Drug Administration who was widely praised for addressing tobacco addiction during his term in office, has joined the struggle against obesity. In a recently available book, he demands retraining our brains, suggesting that people must make the exact same change in societal attitudes toward the acceptability of eating calorie-rich foods that people did toward the acceptability of smoking. He challenges our society to trade the transient neurologic reward of high-sugar/high-fat foods for healthier eating, while acknowledging his own lifelong struggle to resist those very foods. However intellectually appealing his arguments may be, experience, including his own, suggests these behavioral changes are difficult to keep long-term, and the data from neuroimaging studies confirm a formerly obese individual’s neurobiology may be making a silent but very powerful opposition to such change. For some would-be dieters, an ice cream soda will continue to check more desirable than brussels sprouts, and their own neurotransmitters will continue steadily to urge them in the direction of the fats and sugars that will bring satiation and neurologic reward. A current article in the New Yorker reviewed a number of the societal factors that also militate against dietary behavior change, including a decline in the expense of fats, oils, and sugars relative to other foods, and the successful commercial promotion of larger servings extending even into the home, as newer editions of old standby cookbooks now calculate fewer servings from standard recipes.