'20/20' Busts 10 Body Myths

June 23, 2006 — -- When should you begin checking your blood pressure? Is your sunscreen really giving you the protection you think it is?"20/20" teams up anti-aging guru Dr. Michael F. Roizen and heart surgeon Dr. Mehmet Oz, authors of "You: The Owner's Manual" to debunk 10 body myths -- from why you gain weight to aging and memory.

Here are the body myths we debunked with our health experts and the truth behind them.

A lot of people believe that we use only 10 percent of our brain. Is that true?

"It's not true. In fact, you'd be in big trouble if you only used 10 percent. The reality is that we use all of our brain, but we don't use it all the time," said Dr. Oz.

"The brain was really hidden from us until we had new technologies that could allow us either to operate on the brain, or to see what the brain does when you're actually thinking or doing tasks."

Thanks to these advances, we can now see how challenging your mind can keep your brain young. Suzanne, who speaks four languages fluently -- English, Swiss-German, French, and German -- was recently diagnosed with a brain tumor in the language center of her brain. The problem is trying to remove the tumor without destroying her ability to speak her languages. Her treatment will give doctors at UCLA a rare opportunity to literally see how learning a language exercises the brain.

During surgery to remove the tumor, Suzanne, at one point, was awakened. She was shown pictures and asked to identify them in each of her languages.

An MRI lights up the part of the brain that Suzanne uses as she speaks. This helps the surgeon avoid the language area when removing the tumor. But the doctors discover something quite amazing -- each of Suzanne's languages resides in a different part of her brain.

The surgery is successful -- the tumor is removed and Suzanne's knowledge of four languages is saved. Her case busted a big brain myth -- that language resides in just one tiny area of the brain. Because Suzanne learned her languages at different ages, her brain stored them in different places -- showing that challenging your brain creates new neural pathways.

"Just like you challenge a muscle to grow it, well, the brain gets new connections," said Dr. Roizen.

And that busts another big brain myth -- that you can't teach an old dog new tricks. Memory loss is not inevitable. Want to keep your brain young? Exercise it.

Try learning to play a musical instrument, doing crossword puzzles, learning a language -- even playing computer games.

"The data now indicate that an hour of games for 40 weeks can make your brain equivalent, your brain's real age, 10 years younger," Roizen said.

And one final brain myth: Does the size of a person's brain have anything to do with their intellectual capacity?

"There is no correlation with the size of a human brain and its intellect. In fact, Einstein was sort of a famous example. His brain was about average size -- no difference between his and almost any other brain," Oz said.

We've all heard for years that people who are thin have won the biological lottery. They look like they can eat whatever they want without gaining a pound. We think they're lucky to have a high metabolism.

"It's generally false that your metabolism is the reason for your weight," said Oz. "And this has been looked at numerous times."

To figure this out, we turned to Dr. Jim Levine, an obesity researcher at the Mayo Clinic, who's studied the metabolism of lean and heavy people, such as lean Kathy Strickland and a heavier Dawn Campion.

"Dawn's numbers are actually higher because we find continuously is that people with weight problems who have obesity have a higher basal metabolism compared to people who are lean," Levine said.

"Your basal metabolism is the calories you burn to keep your body going, so if your body is bigger of course your basal metabolism is greater," Levine said. "If your body is smaller your basal metabolism is less."

So if a slow metabolism isn't solely to blame, why is it some poeple gain weight and others don't. "People with obesity have a tendency to be seated, a natural tendency to be seated for two-and-a-half hours per day more," Levine said.

It adds up tp 350 calories a day or 30 to 50 pounds a year. Dr. Levine says it isn't about sweating at the gym. It's simple things like walking to your car or playing with your kids Levine believes people can combat obesity by simply moving more. Even standing up at your desk can increase your metabolism by up to 40 percent if you're moving around.

"We're talking about shaking up everything we do because we have no choice in it," Levine said. "Obesity is collapsing corporations in America, but much more importantly, it's devastating our health and it's taking over our children. We have no choice but to do something. We have no choice but to do something big."