The researchers came to their findings by analyzing body mass index (BMI) and waist-to-hip ratio. They found that higher BMI and higher waist-to-hip ratio was associated with lower brain volume.
BMI is calculated by dividing a person’s weight by the square of their height. Obesity is considered a BMI over 30. Waist-to-hip ratio is determined by dividing waist circumference by hip circumference. Having a larger belly leads to a greater waist-to-hip ratio. A ratio greater than 0.90 in men and 0.85 in women is considered centrally obese.
Study author Mark Hamer explained, “Existing research has linked brain shrinkage to memory decline and a higher risk of dementia, but research on whether extra body fat is protective or detrimental to brain size has been inconclusive. Our research looked at a large group of people and found obesity, specifically around the middle, may be linked with brain shrinkage.”
The study looked at 9,652 people with an average age of 55. Nineteen percent of participants were considered obese. BMI, waist-to-hip ratio, and other factors of health were measured. MRI was used to determine brain volume for grey and white matter and volumes in other areas of the brain.
After adjusting for other factors which could contribute to a decline in brain volume, the researchers found that a high BMI was associated with slightly lower brain volumes. High BMI and waist-to-hip ratio were linked with lower grey matter brain volumes. There was no significant difference in the white matter.
Hamer added, “While our study found obesity, especially around the middle, was associated with lower gray matter brain volumes, it’s unclear if abnormalities in brain structure lead to obesity or if obesity leads to these changes in the brain. We also found links between obesity and shrinkage in specific regions of the brain. This will need further research, but it may be possible that someday regularly measuring BMI and waist-to-hip ratio may help determine brain health.”
The results may not be applicable to the general population because only five percent of participants actually took part in the study. Among those who did participate, they tended to be healthier than the general population. Therefore, although the study sheds light onto a possible link between BMI and waist-to-hip ratio to brain volume, additional research on a larger scale needs to be conducted.
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