Fascinating new findings: Obesity starts in the brain
Even a short-term intake of highly processed, unhealthy foods can lead to serious changes in the brain
The proportion of obese people has increased rapidly in recent decades and poses enormous challenges for those affected, healthcare systems and those treating them. The hormone insulin plays a key role in the development of morbid obesity. Until now, there have been many indications that insulin leads to metabolic and neurodegenerative diseases, particularly in the brain. Now a study by the University Hospital of Tübingen, Helmholtz Munich and the German Center for diabetes Research (DZD) provides fascinating new insights into the role of the brain as a crucial control center and the origin of obesity and type 2 diabetes.
Although it has long been known to trigger numerous diseases such as diabetes, heart attacks and even cancer, obesity has only been officially recognized as a disease in its own right in Germany since 2020. With around 16 million people in Germany alone and more than one billion people worldwide, morbid obesity has already been described as an epidemic by the World Health Organization. Obesity is defined as a body mass index of over 30, and a lack of exercise and an unhealthy diet are often considered to be the cause of this chronic disease. However, the mechanisms in the body that lead to obesity and occur in the disease are more complex.
Obesity and the role of insulin in the brain
The brain's sensitivity to insulin is linked to long-term weight gain and unhealthy body fat distribution. What processes exactly take place in the brain and what effects does the insulin action in the brain have on people of normal weight? Prof. Dr. Stephanie Kullmann from the Tübingen University Hospital for Diabetology, Endocrinology and Nephrology and her team got to the bottom of this question in their study. "Our results show for the first time that even a short-term intake of highly processed, unhealthy foods (e.g. chocolate bars and potato chips) leads to a serious change in the brain of healthy people and this can be considered the starting point of obesity and type 2 diabetes," explains study leader Prof. Kullmann. In a healthy state, insulin has an appetite-suppressing effect in the brain. However, in people with obesity in particular, insulin no longer regulates eating behavior properly, resulting in insulin resistance. "Interestingly, in our healthy study participants, the brain shows a similar decrease in sensitivity to insulin after a short-term high calorie intake as in people with morbid obesity," says Ms. Kullmann.
"This effect can even be observed one week after returning to a balanced diet," she adds. She is also deputy head of the Metabolic Neuroimaging department at the DZD partner Institute for Diabetes Research and Metabolic Diseases (IDM) of Helmholtz Munich at the University of Tübingen.
Focus on the brain
"We assume that the brain's insulin response adapts to short-term changes in diet before any weight gain occurs and thus promotes the development of obesity and other secondary diseases," concludes Prof. Dr. Andreas Birkenfeld, Medical Director of Internal Medicine IV, Director of the IDM and DZD Board Member and last author of the study. Based on the new findings, he calls for research into the contribution of the brain to the development of obesity and other metabolic diseases to be intensified.
Short period with far-reaching effects
The study involved 29 male volunteers of normal weight, who were divided into two groups. The first group had to consume an additional 1500 kcal in the form of highly processed, high-calorie snacks on five consecutive days in addition to their normal diet. The control group abstained from the additional calories. After an initial examination, both groups were examined at two different times. One examination took place directly after the five-day phase and a second took place after the first group had returned to their normal diet for seven days. Using magnetic resonance therapy (MRI), the researchers examined the insulin sensitivity in the brain and the fat content of the liver. Not only did the fat content of the liver of the first group increase significantly after five days of increased calorie intake. Surprisingly, the significantly lower insulin sensitivity in the brain compared to the control group also persisted one week after returning to a normal diet. This effect had previously only been observed in morbidly obese people
Note: This article has been translated using a computer system without human intervention. LUMITOS offers these automatic translations to present a wider range of current news. Since this article has been translated with automatic translation, it is possible that it contains errors in vocabulary, syntax or grammar. The original article in German can be found here.
Original publication
Stephanie Kullmann, Lore Wagner, Robert Hauffe, Anne Kühnel, Leontine Sandforth, Ralf Veit, Corinna Dannecker, Jürgen Machann, Andreas Fritsche, Nobert Stefan, Hubert Preissl, Nils B. Kroemer, Martin Heni, André Kleinridders, Andreas L. Birkenfeld; "A short-term, high-caloric diet has prolonged effects on brain insulin action in men"; Nature Metabolism, 2025-2-21
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