How Short-Term Overeating Disrupts Brain Function and Fuels Obesity: Study
New Delhi: Just five days of indulging in ultra-processed high-calorie foods can rewire the brain’s insulin response, paving the way for obesity and metabolic disorders even after returning to a normal diet.
A new study by University Hospital of Tubingen, the German Centre for Diabetes Research (DZD), and Helmholtz Munich has found that consuming high-calorie, ultra-processed foods for a short period can significantly alter brain insulin sensitivity and increase liver fat, effects that persist even after resuming a regular diet.
The findings published in the journal Nature Metabolism provide crucial insights into how the brain regulates metabolism and may contribute to obesity and type 2 diabetes.
Obesity has long been associated with serious health risks, including type 2 diabetes, cardiovascular disease, and cancer. Although it was officially recognized as a disease in Germany in 2020, the World Health Organization (WHO) had already declared obesity an epidemic, affecting over a billion people worldwide and nearly 16 million in Germany alone.
While poor diet and lack of exercise are well-known contributors, scientists emphasize that the biological mechanisms underlying obesity are more complex.
The brain’s sensitivity to insulin plays a critical role in weight regulation and fat distribution. Insulin is known to suppress appetite in healthy individuals, but in people with obesity and insulin resistance, the brain no longer responds properly to insulin signals, leading to overeating and weight gain.
"Our findings demonstrate for the first time that even a brief consumption of highly processed, unhealthy foods (such as chocolate bars and potato chips) causes a significant alteration in the brain of healthy individuals, which may be the initial cause of obesity and type 2 diabetes," said Prof. Dr. Stephanie Kullmann, from Tubingen University Hospital for Diabetology, Endocrinology, and Nephrology.
Interestingly, the study found that even healthy individuals developed insulin resistance in the brain after just five days of high-calorie intake—a phenomenon previously observed only in people with obesity.
"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 obesity," added Prof. Kullmann. "This effect can even be observed one week after returning to a balanced diet."
The study involved 29 healthy-weight male participants, split into two groups. One group consumed an extra 1,500 kcal per day from ultra-processed snacks, such as chocolate bars and chips, for five consecutive days, while the control group maintained their usual diet without additional calories.
Researchers conducted two MRI scans to measure liver fat content and brain insulin sensitivity; one immediately after the five-day period and another seven days after resuming a normal diet.
The results were striking: liver fat content significantly increased after just five days of high-caloric intake, while brain insulin sensitivity remained impaired even after one week of normal eating. These changes mirrored patterns typically observed in obese individuals.
"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," said Prof. Dr. Andreas Birkenfeld, Medical Director of Internal Medicine IV, Director of the IDM, and DZD Board Member.
The findings challenge the traditional notion that obesity is simply a result of excess calories and lack of exercise. Instead, they suggest that even short-term exposure to unhealthy foods may have lasting effects on brain function, making individuals more vulnerable to weight gain and metabolic diseases in the long run.
Prof. Birkenfeld emphasized the need for further research to understand how the brain influences metabolism: "We urge more research on how the brain contributes to the development of obesity and other metabolic illnesses in light of the current findings."
This study underscores the importance of diet quality, not just in terms of weight gain, but also in how the brain regulates hunger and metabolism. It suggests that even short-term dietary indulgences could trigger long-lasting effects that increase the risk of obesity and related diseases.
With obesity and metabolic disorders rising globally, understanding the brain’s role in regulating insulin and metabolism could lead to new strategies for prevention and treatment.
This research reinforces the urgent need for mindful eating habits to maintain brain health and metabolic balance in the fight against obesity and type 2 diabetes.