ScienceEyeroll

"...Over the years, various researchers have shown that caloric restriction can extend life in bats, dogs, and even spiders, and on down to nematode worms and single-celled organisms like yeast. After decades of work, it remains the only way known to increase maximum lifespan [...] In the 1990s, Leonard Guarente of MIT discovered a class of longevity genes in yeast called sirtuins that appear to be activated by a lack of food. Sirtuins appeared to be “conserved” in evolution, meaning that they appear in nearly all species, on up to humans. Sirtuins are thought to have evolved as a way to enable animals to survive periods of famine. They seem to work by regulating certain metabolic pathways and reduce the amount of damage cells endure.

It appeared, then, that caloric restriction seems to activate some sort of deep survival mechanism common to nearly all life forms. If researchers could somehow identify and isolate that mechanism, they’d be that much closer to some kind of longevity pill. Except for one inconvenient fact: Caloric restriction itself does not always work." 

(emphasis mine)

From Slate