What worries people most about growing old? It's not wrinkles and gray hair. It's something far less superficial.

About one-third of 28,000 respondents in an MSNBC online aging poll said they are most worried about their ability to take care of themselves. One-fifth said they're afraid of losing their mental abilities, and 16 percent are afraid they'll grow very ill and experience a lot of pain. Only seven percent fear looking old and wrinkly.

The biggest priority for nearly 60 percent of respondents: Staying strong and healthy.

More than half of the participants report doing all they can to lead a long and healthy life by eating right, exercising, and taking other preventative measures. Less than 10 percent admit they'd rather live a life on the edge, enjoying rather than depriving themselves of indulgences.

S. Jay Olshansky, a professor of public health and a researcher at the Center on Aging at the University of Illinois at Chicago, says he's surprised by the high percentages regarding healthy living, given the fact that two-thirds of Americans are obese or overweight. Are you surprised?