It seems there is a gene variant that in the US is found in half of all people of European ancestry, a quarter of Hispanics, and 15% of Asians and African Americans that causes them to gain weight and "puts them at risk for obesity." Now they find that this same allele is associated with a loss of brain tissue, an average of 8% less in the frontal lobes. People without the bad allele can get fat without losing brain tissue.
That's a third of the population, which makes this a huge candidate for figuring out how the allele works and how to counteract it. Imagine if we were able to take a third of our people and make them not become fat.
I wonder when the brain loss starts and how much it affects cognition. Imagine if a third of our old people didn't have shrinking brains. That would sure reduce the Fox News audience.