Excess weight makes you look older. Especially men.

Excess weight compromises health and quality of life in many ways. It increases the risk of diseases such as diabetes, cardiovascular disease, and cancer. But it does even more: obesity and overweight appear to accelerate aging. This is suggested by two recently published studies, which investigated the connection between high body mass index, brain aging, and physiological decline, identifying significant effects especially among younger people.

The Italian contribution

The first of the two studies was published in the journal eBioMedicine by a team of researchers from several American universities, in collaboration with the University of Bologna. This is the largest international study conducted to date on the relationship between body weight and brain health, involving over 46,000 people across 15 research projects.

The research stems from an observation: it is now known that weight gain in adulthood is associated with a higher risk of developing dementia. It is therefore believed that a high body mass index may affect brain integrity, causing gray and white matter atrophy and affecting the robustness of neural circuits, but the mechanisms that could drive these processes are currently unknown. And this is what the new study aimed to uncover.

Weight and brain health

The research was conducted by performing MRI scans of the participants' brains and using machine learning tools to identify those with markers of aging and brain atrophy. The results were then analyzed taking into account each participant's body mass index.

"From the in-depth analysis of this large number of brain MRIs, it emerged that there is a connection between obesity and brain aging: a phenomenon more pronounced among men than among women, and with effects that diminish with age," explains Filippos Anagnostakis , first author of the study, a research affiliate at the University of Pennsylvania and Columbia University, and a recent medical graduate from the University of Bologna. "The results we obtained," he adds, "are a valuable opportunity for reflection: they invite us to rethink the impact of obesity not only from an aesthetic perspective, but also in relation to brain health."

Greater effects for men

Results show that the brains of young males are most affected by excess weight: being overweight is associated with an average brain age of eight months compared to that of their peers of normal weight, while obesity is associated with a brain age of two years. For women, however, the data show a less clear picture. "We know that gender differences affect the risk of developing dementia differently," says Anagnostakis, "but the pathways that cause these differences remain unclear."

Biological age also increases

The second study, from the University of Chile in Santiago, analyzed the presence of molecular markers of aging in 205 volunteers followed from 1992 to 2022 as part of the Santiago Longitudinal Study, a prospective study that periodically monitored participants' weight and health. The study included 89 people of normal weight, 43 who had been obese since adolescence, and 73 who had begun to suffer from the condition in early childhood. It demonstrated that excess weight that persists from early life causes a measurable increase in biological age: from 2.23 to 4.68 years more around the age of 30, varying depending on how long the individual has been obese and the parameter used for assessment.

Calorie restriction and aging: a paradigm shift?

The findings therefore indicate that living with excess caloric intake and excess weight affects all known markers of aging. For some experts, these findings are strong enough to warrant rethinking some of the cornerstones of what we consider the relationship between nutrition, aging, and health. "The mean biological age is clearly elevated in the two groups that experienced long-term obesity," writes Antonello Lorenzini , Professor of Nutritional Biochemistry at the University of Bologna, in an editorial published in JAMA Network Open . "This increase suggests that it is time to reconsider the interpretation that has long dominated the biology of aging: that is, that calorie restriction slows the aging process. It is now reasonable to hypothesize that it is the excess calories that precede or accompany obesity, or obesity itself, or a combination of these two aspects, that accelerate the aging process."