The Tweet: “Bacon affects the brain the same way as cocaine, overloading pleasure centers in the brain and requiring increasing amounts to be satisfied.”

Obese rats that were allowed to feast on fatty foods displayed compulsive feeding behaviour thought to be triggered in a similar way to cocaine or heroin addiction. In a study published in Nature Neuroscience in 2010, researchers observed that striatal dopamine D2 receptors in the obese rats were downregulated in a similar way to humans addicted to drugs, and complete inhibition of these receptors rapidly accelerated the development of an addiction. The striatum is a core component of the brain’s reward circuit. Here, the released neurotransmitter – dopamine – forms part of the reward feedback loop that tells our brains to reinforce a behaviour. However, with fewer dopamine D2 receptors it requires more and more fatty foods for the obese rats to complete the loop.

In this study rats were divided into three groups: one fed on normal rat food, one allowed access to fatty foods for one hour a day and one allowed access to fatty foods for 23 hours a day. As you would expect, the latter group soon became obese. The group that had access to large quantities of bacon, cake, frosting and other ‘cafeteria-style’ foods found themselves stuck in a vicious cycle of fattening, as the foods effect lessened over time. “Activation of the striatum in response to highly palatable food is blunted in obese individuals when compared with lean controls,” write the authors.

Previous research has linked obesity in rats to reduced levels of D2 receptors. Fewer receptors will mean a lower dopamine uptake and therefore a smaller ‘reward’. These observations led researchers to the proposal that deficits in reward processing may be an important risk factor for the development of obesity, and obese individuals may compulsively eat in order to compensate for their reduced rewards.

Each group of rats was then administered an electric shock during eating to discourage the behaviour. The obese, compulsive eating rats were not deterred by this and continued to eat the fatty foods while the other groups stopped. The reward for eating was stronger than the negative stimulus of the shock.

“People know intuitively that there’s more to [overeating] than just willpower,” writes Paul Kenny, co-author of the study. “There’s a system in the brain that’s been turned on or over-activated, and that’s driving [overeating] at some subconscious level.” The researchers compared the struggle obese individuals have with controlling their diet and their own desire to limit their food intake with the compulsive behaviour of drug addicts.