We Americans aren't the only ones who have gained weight. Over the past 25 years, our cars have gotten heavier too, says Amory Lovins.

Lovins, chief scientist of the Rocky Mountain Institute, says he believes that ultralight materials like carbon fiber composites can make cars simpler and cheaper to build. At the Cleantech Forum in San Francisco this week, Lovins talked about strategies to make oil-free automobiles.

This video originally appeared on SmartPlanet with the headline "Amory Lovins: Carbon fiber cars would cut oil dependency."

More SmartPlanet links