Excess Body Fat Linked with Smaller Brain Size in New Study

A new study out of the United Kingdom has found that those who have a little extra body fat—especially around the belly—may also have a smaller brain size. More importantly, the study suggests that this could put some folks at higher risk for dementia. 

Researchers at Loughborough University studied 9,652 adults, with an average age of 55, by using magnetic resonance imaging (MRI) to measure their brain volumes.  Specifically, the MRIs were measuring white and grey brain matter volume. 

Attempting to discern the potential relationship between extra weight and brain volume, the researchers also measured participant obesity via body mass index (BMI).  BMI is a weight-to-height ratio calculated by dividing weight by the square of height.  This measure is a better indicator of obesity and health risk than simply looking at weight, alone.  As such, a BMI higher than 30 is considered obese.

Next, the researchers measured participant waist-to-hip ratio.  This is a measurement determined by dividing the circumference of the waist by the circumference of the hip (a common ratio in attire sizing).  This is also another measure that is better at helping determine obesity than weight alone. The higher this ratio, the closer you are to obesity: for men the ratio is 0.9 and above and for women the ratio is 0.85 and above. 

Adjusting for other factors that can affect brain volume—age, smoking, hypertension, physical activity, etc—the study did appear to find that a high BMI was associated with slightly lower grey matter volume than a healthy BMI.  The study also found that those with both high BMI and high waist-to-hip ratio had a significantly lower grey brain matter than those with a higher ratio. 

This is important because grey matter is where most of the nerve cells live within the brain.  This includes those brain regions involved with self-control and muscle control as well as sensory perception.  White matter, on the other hand, contains the nerve fiber bundles that connect the various brain regions. 

Study author Mark Hamer, PhD comments, “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 results of this study have been published in the medical journey Neurology.