As obesity rates continue to climb around the world, scientists are trying to better understand how carrying excess weight affects more than just the body—especially how it impacts the brain and cognitive health.
New research led by Professor Anqi Qiu from the Hong Kong Polytechnic University offers a clearer picture of how different long-term patterns of obesity may influence brain function and aging. The findings, published in Nature Mental Health, provide important insights into how managing weight over time could help protect the brain as we age.
Obesity has already been linked to problems with memory, attention, and decision-making, as well as a higher risk of diseases like Alzheimer’s and Parkinson’s. But much of the past research was limited because it looked at people only at one point in time.
This made it difficult to tell whether someone’s weight was a long-term issue or just a temporary condition. It also left a gap in understanding whether brain changes are more closely tied to the amount of weight someone carries or how long they’ve been carrying it.
To fill this gap, Prof. Qiu and her team carried out a long-term study using data from the UK Biobank, a massive health database with over 500,000 participants aged 40 and up. This allowed them to study not just weight and body measurements, but also brain scans and cognitive test results across time.
Based on the data, the team identified five different obesity “trajectories”—or patterns of change over time. These were: low-stable (consistently low body fat), moderate-stable, high-stable, increasing (gaining weight over time), and decreasing (losing weight over time).
The brain-related differences between these groups were striking. People in the decreasing weight group—those who lost weight—showed minimal negative effects on brain structure and cognitive performance when compared with people in the low-stable group. This suggests that weight loss may help reverse or avoid some of the brain changes linked to obesity.
But for the other groups, especially those who gained or consistently carried more weight, the story was very different. In the increasing group, the earliest signs of brain changes appeared in areas that help manage reward, motivation, and emotions. These include the fronto-mesolimbic regions, which play a key role in both eating behavior and brain aging.
In the moderate-stable group, changes spread to regions important for attention and memory, such as the parietal and temporal lobes. And in the high-stable group—those who were persistently obese—these brain changes were widespread and affected multiple areas, including those involved in complex thinking and coordination.
This progressive pattern suggests that the longer someone lives with obesity, the more damage may be done to the brain. The researchers believe that consistent or worsening obesity could actually speed up brain aging. In fact, the team suggests that long-term obesity might even serve as a warning sign or “biomarker” for cognitive decline.
Professor Qiu emphasized the urgency of this research, noting that as people live longer, the number of individuals suffering from brain-related diseases is also increasing.
“There has been a notable rise in neurodegenerative diseases, such as Alzheimer’s disease and Parkinson’s disease, that currently lack a cure,” she said. “This research proposes that maintaining long-term weight control can contribute to improved brain health.”
The results highlight the importance of early intervention and long-term strategies for managing weight—not just to prevent diabetes and heart disease, but to protect the brain as well. Importantly, this research used data from people of diverse ethnic backgrounds, giving it broad relevance across different populations.
Looking ahead, Prof. Qiu and her team plan to explore the biological processes behind these findings using a “multi-omics” approach.
This means they will examine genes, proteins, and other biological factors to better understand how obesity affects the body and brain together. This may eventually lead to more precise and personalized treatments for preventing or slowing brain aging.
In summary, this study shows that long-term patterns of obesity—especially sustained or increasing weight over time—can significantly impact brain health and cognitive function. The good news is that reducing weight, even later in life, appears to protect the brain.
This adds to the growing evidence that maintaining a healthy weight is not only good for the body—it’s crucial for the mind too.
If you care about weight loss, please read studies that hop extract could reduce belly fat in overweight people, and early time-restricted eating could help lose weight.
For more health information, please see recent studies that Mediterranean diet can reduce belly fat much better, and Keto diet could help control body weight and blood sugar in diabetes.
The research findings can be found in Nature Mental Health.
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