Caloric Restriction, the limiting of caloric intake while maintaining normal levels of all other vital nutrients, has been shown to be the only reliable method to significantly extend an animal's lifespan by slowing the process of ageing. A new NY Times article about CR explains the idea fairly well. This is a short FT article from June.
Many people have begun CR diets in an attempt to extend their best years. The Caloric Restriction Society is an organisation which promotes and supports CR.
As touched on in the NY Times article, CR research has the potential to reveal many of the genetic pathways for senescent processes, and in turn, new anti-ageing drugs may come from such research.