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In a groundbreaking new study, researchers at the Institute for Diabetes Research and Metabolic Diseases of the Helmholtz Center Munich, in collaboration with the German Center for Diabetes Research, have uncovered striking evidence that a short-term high-caloric diet can have long-lasting impacts on brain function. The study, published in Nature Metabolism, reveals that consuming an ultra-processed, high-caloric diet for just five days impairs the brain’s insulin responsiveness and increases liver fat in young, healthy men—effects that extend beyond the overeating period itself.
Key Findings of the Study
The study, titled “A short-term, high-caloric diet has prolonged effects on brain insulin action in men,” involved 29 healthy male participants aged 19–27 years with normal body weight (BMI 19–25 kg/m²). The participants were divided into two groups: an experimental group consuming an additional 1,500 calories daily from ultra-processed snacks, and a control group that maintained their usual diets. Over the course of just five days, those in the high-caloric diet (HCD) group increased their daily intake by an average of 1,200 calories, resulting in a significant rise in liver fat content. Surprisingly, these changes occurred without any noticeable differences in body weight or peripheral insulin sensitivity.
Functional magnetic resonance imaging (fMRI) was used to measure the brain’s insulin responsiveness, both during and after the intervention. Even after returning to their regular diet for a week, participants from the HCD group showed decreased insulin activity in several regions of the brain, including the hippocampus and fusiform gyrus, which are important for memory and recognition. The study also observed a concerning reduction in white matter integrity, a key measure of brain structure, following the diet intervention.
Impact on Reward Learning and Cognitive Functions
In addition to insulin resistance, the study found that the high-caloric diet disrupted the brain’s reward learning response, a cognitive process that helps regulate motivation and decision-making related to food choices. Participants in the HCD group demonstrated a reduced sensitivity to rewards, which could prime the brain for long-term unhealthy eating patterns. These effects were particularly concerning, as they resemble patterns commonly seen in individuals with obesity.
The researchers assessed reward processing through a reinforcement learning task, where participants had to respond to cues associated with either positive (reward) or negative (punishment) outcomes. Following five days of consuming calorie-rich snacks, those in the HCD group displayed decreased reward sensitivity, suggesting that the brain’s reward system had become less responsive to positive outcomes, potentially increasing the risk of overeating in the future.
Long-Term Implications
The findings of this study provide crucial insight into the brain’s response to ultra-processed food, even in individuals who are healthy and of normal weight. Insulin resistance in the brain has long been associated with obesity, type 2 diabetes, and cognitive decline, and this study suggests that short-term overeating can trigger these harmful processes before any outward signs of weight gain appear.
“These results suggest that even short-term, high-caloric intake can change brain function in a way that may promote unhealthy eating habits in the long term,” says lead researcher Stephanie Kullmann. “This emphasizes the importance of understanding how diet influences brain function and metabolism.”
Disclaimer
The study’s results are based on a small sample of healthy-weight male participants and may not directly apply to all populations. Further research is required to confirm whether similar effects occur in women or in individuals with pre-existing conditions such as obesity or diabetes. It is important to consult with healthcare professionals before making significant changes to dietary habits.
