![]() ![]() Might there be some tipping point, at which higher reward sensitivity gets eroded too far, into lower sensitivity? There could be a transition in obesity, as has been suggested for addiction, where overconsumption of appetizing foods is initially driven by reward, but then becomes less reward driven and more automatic and compulsive over time. In order to maintain a healthy weight, reward system activation needs to be ‘just right.’ Thus, it is possible that the relationship between reward neurocircuitry and obesity follows the Goldilocks principle – too much or too little reward system activation may lead to weight gain. This is especially true as obesity becomes more extreme. But if you’re obese, the less sensitive you are to rewards, the heavier you tend to be. If you’re a healthy weight or somewhat overweight, the more sensitive you are to rewards, the heavier you tend to be. So both increased and decreased reward sensitivity could lead to obesity? One lab reconciled these seemingly disparate ideas by focusing on sensitivity to reward, a psychobiological trait assumed to be rooted in the dopamine reward system. And our diet may be at least partly to blame: Gobbling down the delicious high-fat, high-sugar foods many of us enjoy appears to reduce the number of dopamine D2 receptors in the brain’s reward circuitry and leads to compulsive overeating. Fewer dopamine D2 receptors result in lower dopamine activity, which has been shown to lead to increased food consumption and weight gain. But some appear to have fewer dopamine D2 receptors in key reward regions of the brain than other people - much like drug addicts. Might there be radically different types of obesity? True, some obese people tend to show high reward activity when viewing food images. ![]() This phenomenon is known as ‘ reward deficiency syndrome’. If you find food less rewarding, in other words, you eat too much in search of finding a ‘normal’ reward experience, and thus gain weight. Following this hypothesis, overeating serves as a compensatory strategy to normalize this reward deficit. “I bet people exhibiting greater activity in brain regions encoding food reward will be at increased risk for obesity!” The more rewarding the food, in other words, the more likely you are to eat too much of it and pack on the pounds.īut there was another camp of researchers who posited that there was decreased, not increased, reward activity in the brains of obese individuals. These are the same regions of the brain activated by addictive drugs and thought to lead to addiction. When neuroscientists scanned the brains of obese individuals viewing images of desirable food, they found greater activity in brain regions rich in dopamine receptors. Genetic risk factors may make some individuals more susceptible to these changes in the environment, and thus more prone to obesity.ĭopamine is an important neurotransmitter that is thought, in part, to mediate reward responses to foods, especially the drive to consume foods. ![]() We now find ourselves in what some term an ‘obesogenic’ environment filled with cheap, easily accessible high-calorie foods served in large portions. What appears to account for this rise in obesity is a complex interaction between genetic and environmental factors. However, there has been a dramatic increase in the prevalence of obesity over the past 50 years, which is far too little time for changes in the genome to have occurred. Some have estimated that 60-70% of the variability in a person’s body mass index or BMI, which is a proxy measure for body fat based on weight and height, is attributable to genetic factors. Genetic factors may play a large role in obesity. Over the following year, those whose brains showed less activation in areas known to respond to natural rewards like foods ended up gaining more weight - though only if they had a particular genetic makeup. Stice’s team had a group of adolescent girls imagine eating appetizing foods while viewing pictures of these foods. But what if I told you that viewing this picture as not rewarding enough might also lead you down the path to obesity?Īn exciting brain imaging and genetics study from the laboratory of Eric Stice at the Oregon Research Institute, recently published in the journal NeuroImage, has shown just that. Before you know it, you may eventually find yourself like 34% of U.S. Research has shown that the more tempting this cake looks to you, the greater the chances you’ll take a bite of real cake, followed by another bite, and another. How pleasurable and desirable does this image of chocolate cake appear to you? ![]()
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