“We propose that highly processed foods share pharmacokinetic properties (e.g. concentrated dose, rapid rate of absorption) with drugs of abuse, due to the addition of fat and/or refined carbohydrates and the rapid rate the refined carbohydrates are absorbed into the system,” write graduate student Erica Schulte and Dr. Ashley Gearhardt of the University of Michigan in PLOS ONE.
The authors characterize addictiveness by factors such as “loss of control over consumption, continued use despite negative consequences, and an inability to cut down despite the desire to do so.” They back up their claims with a study of 504 participants, who helped them assess which foods are hardest to resist.
“Although the causes of obesity are multi factorial, one potential contributing factor is the idea certain foods may be capable of triggering an addictive response in some individuals, which may lead to unintended overeating,” the authors write.
To test the differences between foods, the authors had 120 undergraduate students fill out the Yale Food Addiction Scale, of which Gearhardt was one of the original authors, to determine the individuals’ substance dependence. The students were then shown pictures of 35 common foods, presented in pairs, and asked to say which they considered more likely to produce addiction-like eating behaviors.
Unsurprisingly, foods dense in fat and glycemic load (the amount of carbohydrate in a food multiplied by how swiftly it is converted to sugar) topped the scale. As the authors note, drinks with higher concentrations of alcohol are more addictive than their more diffuse counterparts.
The finding is also consistent with animal studies, which highlight the role of dopamine, our brain’s “pleasure chemical” that’s often implicated in addiction. For instance, rats fed a diet consisting of highly processed foods showed changes to the brain’s dopamine system that’s also seen in response to illicit drugs.
The respondents were segmented in order to explore how gender and body mass index (BMI) alter the difficulty to resist particular food components. Gender was not found to be relevant; people with high BMIs reported addictive-like attraction to more foods, although the correlation was not as strong as might be expected.
Chocolate came up most often, followed by ice cream and french fries.
However, the authors were not convinced they had solved the question of which food is the most craving-inducing. A further 384 people were asked online to rate the addictiveness of each food on a scale of 1 to 7. Using this larger (and more representative) sample, the clear winner was pizza, with a mean score of 4.01, followed by chocolate and chips sharing second at 3.73. Several other foods – all highly processed and rich in sugar, fat or both – were tightly bunched behind. At the bottom of the addictiveness scale came cucumber, carrots and beans. Even water ranked higher than these.
Strangely, however, while the study included soda and water, coffee was not offered among the 35 choices. A match-up between caffeine and pizza’s salt/sugar/fat will have to wait for another time.