Emerging evidence may provide another reason to fight midriff fat
Brain shrinkage is linked to alcoholism, aging, dementia, and chronic stress.
And the brain effects of chronic stress degrade mental performance and emotional health alike.
Stress stimulates release of the hormone cortisol, chronically high levels of which shrink key brain areas, while severe, chronic stress can even kill brain cells.
One of the key brain areas effected most by stress and accompanying cortisol elevation is the hippocampus, which is critical to memory functions.
Chronic stress also affects the structure of the amygdala — an area of the brain that’s key to emotions — in ways that tend to promote anxiety.
For more about the effects of fish and their omega-3s on cortisol levels and brain volume, see Fish Changes Brains for the Better, Omega-3s May Slow Brain Shrinkage, Omega-3s May Expand, Sharpen Brains, Fish Oil Aided Size and Health of Aging Brains, and Brain Benefits of Fish Bolstered by MRI Study.
Previous research linked excess belly fat to brain shrinkage — and the results of a recent British study reinforce those concerns.
British study links belly fat to brain shrinkage
The new findings — based on analysis of data from a prior study — come from two researchers from University College London (Hamer M, Batty GD, 2019).
As the co-author of the new analysis, Mark Hamer, Ph.D., said, “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.”
Hamer and his co-author, G. David Batty, analyzed data from the prior UK Biobank study, which involved 9,652 people: about half men and half women, average age of 55 years, and one in five were obese.
The UK Biobank study had measured each participant’s body-mass index or BMI, waist-to-hip ratio, and overall body fat, and surveyed them about their health.
(People with a BMI above 30 are considered obese. Men with a waist-to-hip ratio above 0.90 and women with a waist-to-hip ratio above 0.85 are said to have “central obesity”.)
The UK Biobank team then used magnetic resonance imaging (MRI) scans to measure the volumes of white and gray brain matter in each participant, as well as the volumes of various regions of their brains.
Gray matter contains most of the brain’s nerve cells, and includes brain regions involved in self-control, muscle control and sensory perception. White matter contains nerve fiber bundles that connect various regions of the brain.
After adjusting for other factors that can affect brain volume — such as age, physical activity, smoking, and high blood pressure — the analysis by Hamer and Batty revealed several links between body composition and volumes of gray and white brain matter:
- Higher BMIs were linked to slightly lower brain volumes.
- Having a higher BMI plus a higher waist-to-hip ratio was linked to smaller volumes of gray matter, versus participants who did not have a higher waist-to-hip ratio.
- Their analysis did not link body composition to significant differences in the volume of white matter.
However, as Hamer said, there's a chicken-or-egg question: “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. 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.”
One limitation of the British study was that only five percent of the people invited to participate in the study took part, and they tended to be healthier than those who did not participate.
Interestingly, the results of preliminary clinical studies suggest that supplemental fish oil may improve body composition: see Omega-3s Linked to Healthier Weight and Body Composition.
- Hamer M, Batty GD. Association of body mass index and waist-to-hip ratio with brain structure: UK Biobank study. Neurology. 2019 Feb 5;92(6):e594-e600. doi: 10.1212/WNL.0000000000006879. Epub 2019 Jan 9.
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