Over the past decade or so, cars began to face an obesity epidemic on their own—even if it's for good reasons, such as all the recent safety improvements, stronger passenger cabin structures, and new interior technologies we've seen. As Autoblog reports, some of Japan's top heads of research and development at automakers have indicated that lighter cars are now a top priority, in order to increase fuel economy and reduce carbon emissions.

The plan: the use of lightweight materials, the reduction of overall size, and the development of new engineering and design methods. No one is expecting all cars to suddenly be made of magnesium or carbon fiber tomorrow morning; that would be prohibitively expensive. But there's a lot that can be done, even now.

The report said that Nissan has already announced plans to reduce vehicle weight by 15 percent by 2015. Plus, Mazda plans to cut 220 pounds from its vehicles beginning in 2011, as they announced a couple of weeks ago. But seemingly more ambitious is Toyota, who is hoping to shed about 400 pounds from the Camry by 2015 or so, according to the article. The company also wants to reduce the Corolla's curb weight by a good 750 to 800 pounds for the car's next generation in 2015. Meanwhile, the 2010 Prius's new engine block (pair of blocks? system?) will be 17 percent lighter and will use a battery pack that's half the weight of the current model, the report said.