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Dopamine: why "just one bite" doesn't work

Posted Dec 21 2011 10:40am

The science on food addiction has now established that highly palatable foods (low-nutrient, high-calorie, intensely sweet, salty, and/or fatty foods - those that make up the majority of the Standard American Diet) produces the exact biochemical effects  in the brain that are characteristic of substance abuse.

Junk food is ubiquitously available, legal, cheap, and socially accepted; therefore, it becomes the drug of choice for many of us.

The following are some characteristics of addiction to a substance or behavior:1

  • Compulsive use of the substance despite negative health and social consequences
  • Tolerance - over time, progressively greater amounts of the substance are needed to reach and maintain the “high”
  • Withdrawal symptoms (link toxic hunger) when the substance is discontinued
  • Activation of reward pathways (including the dopamine system) in the brain

Many of us have had the experience of tasting a junk food or dessert, and then feeling the intense demand from our brain: “MORE!” We feel a complete lack of control, and our commitment to excellent health all of a sudden doesn’t matter. These feelings originate from the dopamine reward system – dopamine is a neurochemical that regulates motivation, pleasure, and reinforcement related to certain stimuli – such as food.  The amount of pleasure we derive from eating a food correlates with the amount of dopamine released in the brain.2

Cookies. Flickr: Rochelle, just rochelle

Obese individuals have a diminished number of dopamine receptors

Obese humans are known to have fewer dopamine receptors (called D2 receptors) compared to lean individuals –their reward response from food is not as sensitive and it is thought that they compensate by overeating.1,3

Overeating blunts the dopamine reward response, encouraging more overeating

Why do obese individuals have lower numbers of dopamine receptors? In substance abuse, over time the brain adapts by downregulating dopamine receptors. It turns out the same happens in overeating.4 A 2011 study revealed that women who had gained a significant amount of weight over a 6-month period reduced their dopamine system response to palatable food over that time period. Similar reductions in the reward response to palatable foods have been reported in women with bulimia nervosa. These results suggest that overeating diminishes the reward from palatable food, driving further overeating and future weight gain.5,7

Desire for highly palatable food is intensified in obese individuals and overeaters

Although actual dopamine reward is diminished in obese individuals compared to lean individuals, dopamine release in response to pictures of palatable food is actually enhanced.4,6

In summary, recent research suggests that overeating and obesity cause greater desire for palatable food, but diminished reward from consuming palatable food - resulting in a progressively worsening addiction.

Our level of susceptibility to addictive behaviors varies by genetic predisposition and emotional state. Nevertheless, highly palatable food has physiologically addictive properties that will make almost anyone experience a lack of control.  “Just one bite” doesn’t work because that single bite activates the dopamine reward system, causing the brain to demand more.  Willpower, logic, and common sense are no match for addictive drives. As with other addictions, recovery requires abstaining from the addictive substance. An alcoholic can’t have “just one drink” without grave risk of relapse. The same is true for food addicts.

Natural plant foods are not as intensely sweet, salty, or fatty as the processed junk foods that are purposely engineered to excite our reward systems.  Eating whole, natural foods provides enjoyment of taste without activating addictive drives.  

Be vigilant this holiday season – stick to the foods that nourish you, and steer clear of any foods that cause you to lose control.   

Note: Addictive drives are powerful. If you are suffering from food addiction, make sure you read Eat to Live  and take advantage of our supportive Member Center  at DrFuhrman.comSupport from others  can help you stay on track with your health goals and prevent relapse.

 

References:

1.         Taylor VH, Curtis CM, Davis C: The obesity epidemic: the role of addiction. CMAJ 2010;182:327-328.

2.         Small DM, Jones-Gotman M, Dagher A: Feeding-induced dopamine release in dorsal striatum correlates with meal pleasantness ratings in healthy human volunteers. Neuroimage 2003;19:1709-1715.

3.         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.

4.         Gearhardt AN, Yokum S, Orr PT, et al: Neural correlates of food addiction. Arch Gen Psychiatry 2011;68:808-816.

5.         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.

6.         Stoeckel LE, Weller RE, Cook EW, 3rd, et al: Widespread reward-system activation in obese women in response to pictures of high-calorie foods. Neuroimage 2008;41:636-647.

7.         Bohon C, Stice E: Reward abnormalities among women with full and subthreshold bulimia nervosa: a functional magnetic resonance imaging study. Int J Eat Disord 2011;44:585-595.

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