Bigger Belly, Shrinking Brain - Each Additional Inch on Your Waist Comes With a Reduction in Gray Matter Volume

Fans of Homer Simpson knew it all along: Abdominal hypertrophy = brain atrophy.

Let me just say something in advance: Neither I, nor the researchers from France, Germany and China who conducted the study at hand and found a correlation between abdominal obesity and the volume of our gray matter are suggesting that all obese men and women are dumb. What we both would probably agree on, though, is the fact that their observations do support a causal relationship between abdominal obesity and a reduced gray matter volume (GMV): "Our findings also provide some evidence that the inverse association between abdominal obesity and brain volume is particularly prominent for GMV, and that it is not mediated by vascular brain injury." (Debette. 2013)
As you can see in figure 1, it is - just as usual - not the BMI that determines the risk of brain-atrophy, but the location and tissue type where the extra-weight is stored.

Figure 1: Association between anthropometric variables and magnetic resonance imaging markers of brain aging; the association with Brain infarcts was not found to be statistically significant (Debette. 2013)

Debette et al. also point out that these associations are not mediated by reverse causation, for instance due to atrophy of brain regions that regulate food intake - a commonly heralded hypothesis in the pertinent literature, by the way.

"The present study, showing a strong inverse association between anthropometric markers of central adiposity and total brain volume, provides further evidence that abdominal fat distribution may be a more powerful predictor of structural brain aging than global body mass, and extends thesefindings to a larger sample of 1779 older persons (mean age 73 years) in the community." (Debette. 2013)

Being abdominally obese is however not the only risk factor for being subject to brain shrinkage. The international team of researchers was also able to confirm a significant association with a certain gene type in women. In view of the fact that this does not change that it's being / getting obese that triggers the brain atrophy, I am yet not willing to waste another word on the "it's not your fault" *bs* - you are not a victim of faulty genes! If anything, you are a victim of flawed information and nutritional advice... but I am digressing.

If we discard the genes, what are the underlying causes?

If you don't want your brain to shrivel away before you are in a coffin six feet under, I suggest you don't miss this post: "Restore & Maintain Insulin Sensitivity - Basics: Turn Your Lifestyle Upside Down" | learn more

Up to now we are not sure, what the exact biophysiological processes may be, but previous research including evidence from longitudinal measurements of brain volumes in overweight or obese individuals undergoing caloric restriction or bariatric surgery suggests that the GMV atrophy can be reversed by caloric restriction - even in the absence of surgery, as a 2009 monkey study by Colman et al. would suggest.

These improvements may be downstream effects of the amelioration of the currently heralded triggers of gray matter volume reductions:

• inflammation,
• insulin resistance and
• adipose-tissue derived hormones, such as leptin

Funny how things will always come down to the usual suspects, isn't it?

Apropos, I did not list it with primary suspects, but actually research by Canessa, et al. (2011), Carnell, et al. (2012) and Morrell, et al. (2010) appears to suggest that sleep apnea, which happens to be correlated with inflammation, insulin resistance and an overabundance of leptin and is about as rampant (yet rarely diagnosed, as obesity) could turn out to be heavily involved in the etiology of brain shrinking, as well.

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Bottom line: If you are stupid enough to let your waist line expand only 0.5cm every year, you better get accustomed to the idea that your brain will be shriveling away faster than your skin. Moreover, this process appears to start early in life, as a study Gunstad et al. who observed similar trends in health individuals from a much broader age spectrum (17-79y) appears to suggest.

And last but not least, a 2005 study by Enzinger et al. confirms that increased HbA1c levels and thus, as Debette et al. suspect insulin resistance and diabetes are likewise significantly associated with an increased risk of brain atrophy.

So in case you haven't done so already, I suggest you read both the information about lifestyle modifications and supplements to improve and maintain insulin resistance.

References:

• Blakemore SJ, Burnett S, Dahl RE. The role of puberty in the developing adolescent brain. Hum Brain Mapp. 2010 Jun;31(6):926-33.
• Canessa N, Castronovo V, Cappa SF, Aloia MS, Marelli S, Falini A, Alemanno F, Ferini-Strambi L. Obstructive sleep apnea: brain structural changes and neurocognitive function before and after treatment. Am J Respir Crit Care Med. 2011 May 15;183(10):1419-26.
• Carnell S, Gibson C, Benson L, Ochner CN, Geliebter A. Neuroimaging and obesity: current knowledge and future directions. Obes Rev. 2012 Jan;13(1):43-56.
• Colman RJ, Anderson RM, Johnson SC, Kastman EK, Kosmatka KJ, Beasley TM, Allison DB, Cruzen C, Simmons HA, Kemnitz JW, Weindruch R. Caloric restriction delays disease onset and mortality in rhesus monkeys. Science. 2009 Jul 10;325(5937):201-4.
• ebette S, Wolf C, Lambert JC, Crivello F, Soumaré A, Zhu YC, Schilling S, Dufouil C, Mazoyer B, Amouyel P, Tzourio C, Elbaz A. Abdominal obesity and lower gray matter volume: a Mendelian randomization study. Neurobiol Aging. 2013 Aug 31. [ahead of print]
• Enzinger C, Fazekas F, Matthews PM, Ropele S, Schmidt H, Smith S, Schmidt R. Risk factors for progression of brain atrophy in aging: six-year follow-up of normal subjects. Neurology. 2005 May 24;64(10):1704-11.
• Gunstad J, Paul RH, Cohen RA, Tate DF, Spitznagel MB, Grieve S, Gordon E. Relationship between body mass index and brain volume in healthy adults. Int J Neurosci. 2008 Nov;118(11):1582-93.