Some interesting research into the roots of longevity gains through calorie restriction: "Working in yeast cells, the researchers have linked ribosomes, the protein-making factories in living cells, and Gcn4, a specialized protein that aids in the expression of genetic information, to the pathways related to dietary response and aging. ... Previous research has shown that the lifespan-extending properties of dietary restriction are mediated in part by reduced signaling through TOR, an enzyme involved in many vital operations in a cell. When an organism has less TOR signaling in response to dietary restriction, one side effect is that the organism also decreases the rate at which it makes new proteins, a process called translation. ... mutations to the ribosome, the cell's protein factory, sometimes led to increased life span. Ribosomes are made up of two parts -- the large and small subunits ... What we noticed right away was that the long-lived strains always had disruptive mutations in the large ribosomal subunit and never in the small subunit ... depletion of the ribosomes' large subunits was likely to be increasing life span by a mechanism related to dietary restriction - the TOR signaling pathway."

Link: http://uwnews.org/article.asp?articleID=41162