Drug addicts' brain reward circuits often exhibit dulled responses, leading the addicts to seek more of the addictive substance to get their fix. Work in rats indicates that fatty foods may trigger similar responses.
Paul Johnson and Paul Kenny at the Scripps Research Institute-Scripps Florida in Jupiter fed rats a high-fat diet, including bacon and sausages, and measured their responsiveness to reward. Animals given prolonged access to the fatty foods needed more stimulation than normal rats to reach a certain reward threshold over time, and gained more weight. Even when the rats were conditioned to associate a light signal with an electric shock to the foot, those with extended access to the high-fat diet continued to eat despite seeing the light, indicating the onset of compulsive-eating behaviour.
When the researchers blocked the expression of a dopamine receptor that is downregulated in human drug addicts, rats consuming the rich diet became compulsive eaters more rapidly.
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Addiction: Junk-food junkies. Nature 464, 652 (2010). https://doi.org/10.1038/464652c