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:
- 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.
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.
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. 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.
