Obesity gene affects brain function

We all know it’s not good for us to gain too much weight. Health consequences such as diabetes, high blood pressure, heart disease and stroke are very well documented and warnings abound. Some evidence also shows that obesity could be linked to negative mental health outcomes as well.
Research identified a link between a fairly common gene variant associated with obesity and less brain volume in certain areas.
The gene variant is known as the FTO gene and almost half of people with European or African heritage carry it. For those who do, it predisposes to weight gain. Individuals with one copy of the gene weigh an average of four and a half pounds more than those without it and people with two copies weigh about nine pounds more than those without. This gene is also expressed in the brain and since some studies have linked higher body mass index with brain volume loss, a group of researchers at the University of California wanted to study whether the gene itself might be associated with brain volumn deficits.
Researchers examined 206 cognitively healthy people between the ages of 70 and 90 who had already been genotyped for a study attempting to identify factors that resist dementia as the brain ages. Results were published in 2010 in Proceedings of the National Academy of Science.  Although the study subjects were comparable in age, education and general health, it was noted that 128 had either one or two copies of the FTO gene while 78 did not. A relatively new MRI technique was used to map brain volume and those with the FTO gene variant had an average of eight percent less tissue in the frontal lobes of their brains. Similarly, FTO carriers had roughly 12 percent less tissue in the occipital lobes of their brains when compared to those without the gene variant.
Even if the FTO gene variant may lead to a reduction in brain volume in some areas of the brain, the question remains whether this has any real-life implications for those individuals.
More research is needed to fully understand the complex relationship, but the authors of this study feel the lower brain volumes may lead to difficulty with executive functioning – a set of brain processes involved in planning, abstract thinking rule acquisition, initiating appropriate actions and inhibiting inappropriate actions, and selecting relevant sensory information.
This hypothesis is made because poor executive function has been linked to frontal lobe deficits in the past and because in general obese individuals are known to have poorer executive function than average. Another possibility is that the FTO gene variant may set the stage for dementia in later life. Other studies have shown obesity as a risk factor for dementia and Alzheimer’s Disease so more research will have to determine whether this particular gene variant is harmful in that respect.
Research into different age groups will also help to further understand the relationship between the presence of this ‘obesity gene’ and brain volume or functional problems.

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About the Author

Paul Latimer has over 25 years experience in clinical practice, research, and administration.

After obtaining his medical degree from Queen's University in Kingston, Ontario, he did psychiatric training at Queen's, Oxford and Temple Universities. After his residency he did a doctorate in medical science at McMaster University where he was also a Medical Research Council of Canada Scholar.

Since 1983 he has been practicing psychiatry in Kelowna, BC, where he has held many administrative positions and conducted numerous clinical trials.

He has published many scientific papers and one book on the psychophysiology of the functional bowel disorders.

He is an avid photographer, skier and outdoorsman.

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