Research demonstrates that obesity is tied to a greater risk of cardiovascular disease and diabetes. Now a new study, published online in Neurology last month, suggests it may also be linked to a decreased volume of gray matter in the brain.
To look at the association between obesity and gray matter volume—the part of the brain that contains most of the neurons essential for functions, such as muscle control and sensory perception—a team of researchers analyzed body composition and brain scan data from 9,652 participants in the UK Biobank database, an observational study of half a million people that investigates the genetic, environmental, and lifestyle factors that contribute to the development of diseases of middle age to later life.
The researchers assessed the participants’ body mass index (BMI)—a formula that includes height and weight, waist-to-hip ratio, and total fat mass—and reviewed their MRI brain scans to measure brain volume. In analyzing the scans, the researchers accounted for age, physical activity, smoking, and high blood pressure—factors that may contribute to reduced gray matter volume.
A BMI score between 18.5 and 24.9 is considered healthy; a score of 30 is considered obese.
A high score for a waist-to-hip ratio—above 0.90 for men and above 0.85 for women—suggests abdominal obesity.
Out of the study sample, 18.7 percent of participants were classified as obese. This group was also less likely to have a college degree and be physically active, and have a higher prevalence of hypertension, diabetes, and heart disease.
Participants who had a high BMI and abdominal obesity had the lowest average of gray matter volume. Obese participants without a high waist-to-hip ratio had a gray matter volume comparable to that of overweight participants. Specifically, obesity was associated with a lower volume in areas of the brain involved in motivation and reward.
The researchers noted that due to the observational nature of the study, they were not able to confirm a causal link between obesity and lower brain volume.
They also could not determine if abnormalities in brain structure contribute to obesity or obesity leads to changes in gray matter volume that can influence the risk of neurodegenerative disease.
Further research is needed to confirm the findings and understand the mechanism behind this association.
For more about the connection between obesity and brain health, read Weighty Matters. For tips on how to lose weight, read Weight Watch.
