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High-glycemic Foods May Fuel Addictive Cravings

photo of walnutsFor most people, hunger is not the only factor that influences eating behaviors, and some have more difficulty regulating their food intake than others. Scientists have proposed the excessively sweet, salty, and/or fatty (“highly palatable”) foods common in the standard American diet can produce addiction-like effects in the human brain, driving loss of self-control, overeating, and weight gain.1, 2 In fact, the behavioral and neurobiochemical characteristics of substance abuse and overeating are quite similar, and the idea of food addiction is becoming more widely accepted among scientists.3-6

Dopamine is a brain chemical that is involved in motivation, pleasure and reward. The dopamine reward system has been shown to be involved in overeating behaviors in animals, and the effects are similar to those of drug dependence.7 Studies on brain activity in humans have provided preliminary evidence supporting the idea that overeating alters the dopamine reward system, which then acts to drive further overeating. Substance abuse is known to reduce the numbers of dopamine receptors (called D2 receptors) in the brain, and this is thought to underlie the tolerance associated with addiction — over time, greater amounts of the substance are required to reach the same level of reward because the reward response has been reduced. Similarly, in the context of food addiction, reduced numbers of dopamine D2 receptors have been reported in obese compared to lean humans, and the dopamine reward response becomes diminished over a period of weight gain.8-11 The dopamine reward response is also reduced among women with bulimia compared to healthy women.12 Frequent consumption of ice cream was shown to reduce the reward response in adolescents.13 Together, these studies imply that overeating results in a diminished dopamine reward response, resulting in a constant cycle of overeating and a progressively worsening addiction to low-nutrient, highly palatable foods.

One new study investigated the relationship between the intensity of the blood glucose response to a certain food and the degree of activity in a reward-related region of the brain. Overweight and obese men were given either a high-glycemic index (GI) or low-GI shake (identical in number of calories and macronutrient distribution), and cerebral blood flow was measured four hours after the meal. The high-GI meal resulted in higher ratings of hunger and greater activation of the right nucleus accumbens, an brain region involved in pleasure, dopamine reward, and addiction.14 This study implies that the size of the blood glucose spike produced by a food correlates to the size of the addictive drive it produces in the brain.

This study provides more support for avoiding refined, high-glycemic foods, such as sugars, white flour products, white potatoes and white rice, because foods with a high glycemic load can promote cravings, possibly in part via the dopamine reward system, especially in those suffering with food addiction and struggling to lose weight. Whereas beans’ low glycemic load promotes satiety, and according to this new research, would reduce the potential for activating reward centers and producing addictive cravings making them the preferred carbohydrate choice.

 


References:
1. Cocores JA, Gold MS: The Salted Food Addiction Hypothesis may explain overeating and the obesity epidemic. Med Hypotheses 2009;73:892-899.
2. Ifland JR, Preuss HG, Marcus MT, et al: Refined food addiction: a classic substance use disorder. Med Hypotheses 2009;72:518-526.
3. Gearhardt AN, Yokum S, Orr PT, et al: Neural Correlates of Food Addiction. Arch Gen Psychiatry 2011.
4. Volkow ND, Wang GJ, Fowler JS, et al: Food and drug reward: overlapping circuits in human obesity and addiction. Curr Top Behav Neurosci 2012;11:1-24.
5. Avena NM, Gold JA, Kroll C, et al: Further developments in the neurobiology of food and addiction: update on the state of the science. Nutrition 2012;28:341-343.
6. Fortuna JL: The obesity epidemic and food addiction: clinical similarities to drug dependence. J Psychoactive Drugs 2012;44:56-63.
7. Johnson PM, Kenny PJ: Dopamine D2 receptors in addiction-like reward dysfunction and compulsive eating in obese rats. Nat Neurosci 2010;13:635-641.
8. Stice E, Yokum S, Blum K, et al: Weight gain is associated with reduced striatal response to palatable food. J Neurosci 2010;30:13105-13109.
9. Wang GJ, Volkow ND, Logan J, et al: Brain dopamine and obesity. Lancet 2001;357:354-357.
10. Taylor VH, Curtis CM, Davis C: The obesity epidemic: the role of addiction. Can Med Assoc J 2009;182:327-328.
11. Volkow ND, Wang GJ, Telang F, et al: Low dopamine striatal D2 receptors are associated with prefrontal metabolism in obese subjects: possible contributing factors. Neuroimage 2008;42:1537-1543.
12. Bohon C, Stice E: Reward abnormalities among women with full and subthreshold bulimia nervosa: A functional magnetic resonance imaging study. Int J Eat Disord 2010.
13. Burger KS, Stice E: Frequent ice cream consumption is associated with reduced striatal response to receipt of an ice cream-based milkshake. Am J Clin Nutr 2012;95:810-817.
14. Lennerz BS, Alsop DC, Holsen LM, et al: Effects of dietary glycemic index on brain regions related to reward and craving in men. Am J Clin Nutr 2013.

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