In a study of 336,309 UK Biobank participants, researchers found that the increased body fat incrementally leads to the increased atrophy of gray matter and consequently the higher risk of declining brain health.
Mulugeta et al. found that middle to elderly age groups (37-73) gray brain matter decreased by 0.3% for every extra 1 kg/m2, which is equivalent of an extra 3 kg of weight for person of average height individuals, (173 cm). Image credit: Marta Cuesta.
“Our findings add to the growing issues associated with being overweight or obese,” said Dr. Anwar Mulugeta, a researcher in the Australian Centre for Precision Health at the University of South Australia, Adelaide, the South Australian Health and Medical Research Institute, and the Department of Pharmacology and Clinical Pharmacy at Addis Ababa University.
“Obesity is a genetically complex condition characterized by the excessive body fat.”
“While the disease burden of obesity has increased over the past five decades, the complex nature of the disease means that not all obese individuals are metabolically unhealthy, which makes it difficult to pinpoint who is at risk of associated diseases, and who is not.”
“Certainly, being overweight generally increases your risk for cardiovascular disease, type 2 diabetes, and low-grade inflammation, but understanding the level of risk is important to better direct supports.”
Using a technique called ‘Mendelian Randomization,’ Dr. Mulugeta and his colleagues analyzed genetic data on 336,309 participants of the UK Biobank project.
The researchers investigated the causal relationships of individuals within three metabolically different obesity types — unfavorable, neutral and favorable — to establish whether specific weight groups were more at risk than others.
Both metabolically unfavorable and metabolically neutral adiposity subtypes were associated with lower gray matter volume.
Metabolically favorable adiposity was tentatively associated with a higher gray matter volume.
“Generally, the three obesity subtypes have a characteristic of higher body mass index, yet, each type varies in terms of body fat and visceral fat distribution, with a different risk of cardiometabolic diseases,” Dr. Mulugeta said.
“We found that people with higher levels of obesity especially those with metabolically unfavorable and neutral adiposity subtypes had much lower levels of gray brain matter, indicating that these people may have compromised brain function which needed further investigation.”
“However, we did not find conclusive evidence to link a specific obesity subtype with dementia or stroke.”
“Instead, our study suggests the possible role of inflammation and metabolic abnormalities and how they can contribute to obesity and gray matter volume reduction.”
“Maintaining a healthy weight is important for general public health,” said Professor Elina Hyppönen, director of the Australian Centre for Precision Health at the University of South Australia and a researcher at the South Australian Health and Medical Research Institute and the UCL Great Ormond Street Institute of Child Health.
“It is increasingly appreciated that obesity is a complex condition, and that especially excess fat which is located around the internal organs have particularly harmful effects on health.”
“Here, we used the individuals’ genetic and metabolic profiles to confirm different types of obesity.”
“In practice, our findings very much support the need to look at the type of obesity when assessing the type of likely health impact.”
“Even in a relatively normal weight individual, excess weight around the abdominal area may be a cause of concern.”
The study was published in the journal Neurobiology of Aging.
Anwar Mulugeta et al. 2021. Unlocking the causal link of metabolically different adiposity subtypes with brain volumes and the risks of dementia and stroke: A Mendelian randomization study. Neurobiology of Aging 102: 161-169; doi: 10.1016/j.neurobiolaging.2021.02.010