In Japan, most Sumo wrestlers weigh 300-400 pounds. While they're professionally active, they follow a diet and workout routine that helps keep them surprisingly healthy, considering their girth.

But once they stop training, they're prone to developing Type 2 diabetes, high LDL cholesterol and cardiovascular disease, and they have a life expectancy that's 10 years shorter than the general population.

It shouldn't take a genius to figure out that sooner or later, being chronically obese is going to exact consequences. That’s how it is with belly fat and brains: If you’ve got one, you're losing the other.

During a study published in the journal Neurology, researchers found that people with the highest body mass index (BMI) and the highest waist-to-hip ratios (fat around the middle) had the lowest volume of brain gray matter. This matter contains most of the brain's nerve cells, memory transmission centers, and synapses.

People with a BMI of 30 or above and a waist-to-hip ratio more than 0.90 for males and more than 0.85 for females had an average gray matter brain volume of 786 cubic centimeters. Those with healthy BMIs and waist-to-hip ratios had an average volume of gray matter of 798 cubic centimeters.

Just being overweight, even without a huge belly, is associated with a smaller hippocampal memory-relay center.

Such gray-matter shrinkage puts you at risk for dementia.