Calorie restriction extends life in most short-lived species where this effect can be measured in a practical amount of time. It is suspected that the effect is smaller in long-lived species such as we humans, but nonetheless calorie restriction produces large benefits to health in human studies, far greater than can be obtained by any presently available medical technology applied to a basically healthy individual. Thus for some years researchers have been working on understanding the exceedingly complex mechanisms of calorie restriction, so as to find out how to recreate the benefits without the reduced calorie intake. It's a challenging task, nowhere near completion: calorie restriction changes just about everything in the operation of metabolism.
This research result, in which researchers shut off part of the life extension of calorie restriction, convincingly adds to the data suggesting that calorie restriction operates through several distinct mechanisms running in parallel:
The roundworm Caenorhabditis elegans lives only about 20 days. This makes it an ideal research subject, as the complete lifecycle of the worm can be studied in a short time. Also, the worm consists of less than a thousand cells, and its genetic make-up has been extensively analysed, and contains many genes similar to humans. [Results] indicate that the receptor NHR-62 must be active for reduced dietary intake to fully prolong the life of worms. If NHR-62 is inactive, Caenorhabditis elegans will live 25% longer under dietary restriction than if this receptor is inactive. "It seems that there is an as yet unknown hormone which regulates lifespan using NHR-62. If we can identify this hormone and administer it to the worm, we may prolong its life without having to change its calorie intake."
A restricted diet also affects the expression of genes dramatically: out of the approximate 20,000 worm genes, 3,000 change their activity, and 600 of these show a dependence on NHR-62. It follows that there are many other candidates for improving life expectancy. Since humans have receptors similar to NHR-62, so-called HNF-4α, the [scientists] suspect that the hormone receptors may not only control the maximum lifespan of roundworms, but might affect human beings as well.