Junk food messes with your brain
When a person does something that is pleasurable, such as eating chocolate, the neurotransmitter dopamine is released in the brain. This reinforces the behaviour, making it more likely for the person to repeat the same action. Dopamine is involved in the brain's reward system, a complex neuronal network responsible for the pleasurable feelings associated with certain behaviours like eating and sex. However, the reward system can also become deregulated, leading to compulsive behaviours, including addiction.
The neural mechanisms underlying junk food hedonism
The REBOST project aimed to investigate the neurological mechanisms behind the effects of excessive junk food consumption on the brain’s reward system, with a special focus on its vulnerability to high-calorie, high-sugar foods. “We were not only interested in what kind of effects consumption of excessive amounts of junk food has on the reward system while exposed to a food reward, but also how it affects the responses to other kinds of rewards, such as a sexual partner,” explains project coordinator Eelke Snoeren. The research was undertaken with the support of the Marie Skłodowska-Curie Actions (MSCA) programme and involved studies in both rats and humans. “In the rat studies, we used a cafeteria (CAF) diet that consisted of a choice of the same unhealthy foods that humans eat in an attempt to recreate the consumption behaviour seen in humans,” outlines the MSCA research fellow Jaume Ferrer Lalanza. Following this dietary intervention, the rats underwent a reward behaviour test where they were presented with either a food or sexual reward. The neural activity in the ventral tegmental area (VTA), an important brain region of the reward system, was monitored throughout the study.
Junk food influences the brain’s reward system
Researchers discovered that rats on a long-term CAF diet eventually developed less interest and ate a smaller amount of a junk food reward than control animals on a healthy diet. “This suggested that the reward became less exciting for them,” emphasises Snoeren. This behavioural effect coincided with alterations in the brain reward system, as shown by the lower neural activity responses in the VTA brain region. In a normal situation, the neural activity in the VTA increases upon sniffing the food reward. Intriguingly, these changes in the brain reward system were also evident when the rats were exposed to a sexual reward. Collectively, REBOST data indicate that junk food consumption desensitises the brain reward system for food rewards, and that more rewards are probably needed to get the same pleasurable effect. These effects are not immediately mitigated by refraining from junk food. “Our work is a small piece in a larger puzzle and further work is needed to study the effects of junk food on other brain regions,” concludes Snoeren. “Nonetheless, it serves as the groundwork for understanding and explaining the underlying mechanisms of obesity and associated mental comorbidities.” Given its high global prevalence, REBOST results will pave the way for further research into novel interventions that can effectively target possible causes of obesity.
Keywords
REBOST, junk food, brain reward system, dopamine, sex reward