What Causes the Brain to Shrink?

No one knows why, but scientist have long seen a correlation between Alzheimer's and loss of brain volume. In other words, the more one's brain shrinks with age, the more likely that person is to suffer from dementia. But what causes the brain to shrink? Scientists are now beginning to believe that an obesity gene, called the FTO gene, may be a possible culprit.

In fact, more than one-third of the U.S. population is at risk for diseases such as Alzheimer's due to a variant of the obesity gene.

Researchers at the University of California, Los Angeles, found the same gene -- allele, from the fat mass and obesity associated gene, the FTO gene, which increases risk of gaining weight -- is also linked to brain shrinkage.

Senior study author Paul Thompson, a UCLA professor of neurology and colleagues said the FTO variant puts more than one-third of the U.S. population at risk for a disease, such as Alzheimer's.

The researchers generated three-dimensional "maps" of brain volume differences in 206 healthy elderly subjects using magnetic resonance imaging from 58 sites in the United States.

The study, published in the journal Proceedings of the National Academy of Sciences, found consistently less brain tissue -- up to less than 12 percent of some parts of the brain -- in those with the FTO allele compared with non-carriers of the variant.

In addition, the study said the differences of brain volume could not be directly attributed to other obesity-related factors such as cholesterol levels, diabetes or high blood pressure.

"If you have the bad FTO gene, your weight affects your brain adversely in terms of tissue loss," Thompson said in a statement. "If you don't carry FTO, higher body weight doesn't translate into brain deficits."

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