Scientists named the most dangerous type of obesity for the brain

Not only the amount of fat in the body but also where it accumulates affects brain health and cognitive abilities. This is the conclusion reached by scientists who analyzed data from more than 18,000 adult participants in the UK Biobank.

The study was published in the journal Nature Mental Health (NMH).

Body mass index (BMI) is traditionally used to assess obesity, but this measure says nothing about the distribution of adipose tissue. Yet fat in different parts of the body can affect health in entirely different ways. A team of researchers led by Anqi Qiu from Hong Kong Polytechnic University set out to determine how fat deposits in various areas of the body are associated with brain structure and function.

More than 18,000 people participated in the large-scale study, with an average age of approximately 62 years. Using dual-energy X-ray absorptiometry, specialists measured the volume of fat in the arms, legs, trunk, and around the abdominal organs — known as visceral fat. The participants then underwent several types of brain magnetic resonance imaging and a series of cognitive tests assessing memory, processing speed, reasoning ability, and executive functions.

The results proved quite telling: different types of fat deposits are associated with different changes in the brain. Visceral fat turned out to be the most dangerous. It showed the strongest correlation with deterioration of the brain's white matter — the network of nerve fibers responsible for transmitting signals between different parts of the nervous system. In people with large amounts of visceral fat, signs of reduced nerve fiber density, fluid accumulation in brain tissues, and disruption of their structural organization were detected.

In addition, the researchers calculated the so-called "brain age" — a measure reflecting the degree of neural network aging. It turned out that accelerated brain aging serves as the primary mechanism through which excess fat undermines cognitive abilities. Across all tests conducted, visceral fat once again demonstrated the most pronounced negative impact on thinking and memory.

According to the study's authors, the findings provide compelling evidence that assessing the risks of age-related cognitive decline requires considering not only a person's overall weight but also where exactly in the body adipose tissue accumulates.