Dietary restriction effectively extends lifespan in mammals and decreases the incidence and progression of many age-dependent diseases. To understand the genetic mechanisms that longevity responses to dietary restriction would have far-reaching impacts on future medical treatments to deal with the ageing problems. Until recently, we knew nothing about these mechanisms in metazoans. Recent advances of the genetic bases of energy sensing and life control in yeast, invertebrates, and mammals have begun to settle the problem. More evidence indicates that the brain has a principal role in sensing dietary restriction and extending lifespan in metazoans. This paper reviews recently development of mechanisms, regulatory factors, genes, nervous control, and related hypothesizes of DR-longevity mechanisms in metazoans.