Why we find it difficult to say no to chocolate, chips and fries

A team from the Max Planck Institute for Metabolism Research in Cologne used the brain activity of test persons to investigate why it is so difficult for us to say no to chocolate, crisps and fries. The study showed that fatty and sweet foods strongly activated the reward system, the institute announced on Wednesday. The brain learns to subconsciously prefer such foods. The results have been published in the journal Cell Metabolism.

“Our propensity for high-fat, high-sugar foods, the so-called Western diet, could be innate or it could develop as a result of being overweight. But we think that the brain learns this preference,” said lead author Sharmili Edwin Thanarajah, explaining the central hypothesis of the study.

To test this, the researchers gave a group of normal-weight subjects a high-fat, high-sugar pudding twice a day for eight weeks in addition to their normal diet. The other group received a pudding that contained the same number of calories but less fat and sugar. Before and during the eight weeks, the team measured the subjects' brain activity.

The measurements showed that the pudding, which was rich in fat and sugar, activated the so-called dopaminergic system of the test subjects particularly strongly. This region of the brain is responsible for motivation and reward. "Our measurements of brain activity have shown that the brain rewires itself through the consumption of fries and the like. It subconsciously learns to prefer rewarding food," said study leader Marc Tittgemeyer. Changes in weight and blood values ​​were not found in the subjects.

The researchers assume that the learned preference will continue after the study. “New connections are made in the brain, which also don’t dissolve so quickly. The point of learning is that you don't forget things you've learned so quickly," explained Tittgemeyer.

The study was carried out in collaboration with researchers from Yale University in New Haven (USA), among others. The team points out that the analysis only provides initial indications, but no certainties, partly because of the relatively small number of test subjects (57). The result can also be different for underweight or overweight people. The same applies to other types of snacks and a different test duration.

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