Based on their research, two biologists have concluded that caloric restriction won't greatly increase lifespan in humans. Their opinion is very similar to that of Aubrey De Grey.

"The trade-off between calories and longevity appears to be close to a linear relationship, but the slope isn't very steep," said Phelan, whose model predicts the relationship between calories consumed and life span.

"Longevity is not a trait that exists in isolation; it evolves as part of a complex life history, with a wide range of underpinning physiological mechanisms involving, among other things, chronic disease processes."

For instance, in mice, starvation reduces fertility, which in turn lengthens life span as the animal is not stressed by repeated matings and pregnancies and the associated production of hormones, they said.