"People who are a little bit overweight have lost about eight percent of their brain tissue," said Dr. Paul Thompson. "That means that they can look about 16 years older."
Over eating alone may be damaging to your brain, but a group of UCLA researchers say 40 percent of Americans carry even more of a risk. Forty-six percent of white Americans have an FTO gene that can lead to obesity.
The gene is less likely to appear in people of African, Latino or Asian descent. Those with the FTO gene are also more likely to have less brain tissue.
Dr. Thompson says the amount of weight that you gain is also related to the amount of brain tissue that you lose. And how long you carry around this extra weight also makes a difference.
"The reason that a high fat diet damages your brain is just that your arteries are full," said Dr. Thompson. "It is the same reason it is bad for your heart. It basically deprives oxygen to the brain."
Those with the FTO variant tend to eat an excess of about 200 calories a day, but research shows you can reverse the effects simply by walking two miles day.
"I'd love to know if I have this gene so I could be more proactive," said West Hollywood resident, Ryan Vandegrientd. "I can watch what I eat a little bit more, and be a little more health conscious."
Companies do offer expensive tests for this gene, but experts say we can all take steps to increase our brain health just by eating right and exercising.
"So long as you can do some kind of physical activity," said Dr. Thompson. "Walking faster and getting your heart rate up is better, but it is not necessary. It is the calories burned that seems to be the main thing."
Again, any loss of brain tissue puts you at greater risk for functional decline. But Dr. Thompson says the public health message here is that a healthy lifestyle will counteract the risk of brain loss whether you carry the gene or not.