Why Eating Less Leads to Longer Lives

For more than 70 years, the Scientific American reports, scientists have known that cutting calories by 30 percent would lead to a longer life, but they never knew why. Until now.
Sciam reports that researchers at Harvard Medical School have found evidence that the phenomenon is likely linked to two enzymes—SIRT3 and SIRT4—in
mitochondria (the cell’s powerhouse that, among other tasks, converts
nutrients to energy). They found that a cascade of reactions triggered
by lower caloric intake raises the levels of these enzymes, leading to
an increase in the strength and efficiency of the cellular batteries.
By invigorating the mitochondria, SIRT3 and SIRT4 extend the life of
cells, by preventing flagging mitochondria from developing tiny holes
(or pores) in their membranes that allow proteins that trigger
apoptosis, or cell death, to seep out into the rest of the cell. According the Scientific American, the researchers determined that lower caloric intake sends a signal that activates a gene
inside cells that codes for the enzyme NAMPT (nicotinamide
phosphoribosyltransferase). The two- to four-fold surge in NAMPT in
turn triggers the production of a molecule called NAD (nicotinamide
adenine dinucleotide), which plays a key role in cellular metabolism
and signaling. The uptick in NAD levels, in turn, activates the SIRT3 and SIRT4
genes, increasing levels of their corresponding SIRT3 and SIRT4
enzymes, which then flood the interior of the mitochondria. Sinclair
says he’s not sure exactly how SIRT3 and SIRT4 beef up the
mitochondria’s energy output, but that events leading to cell death are
at the very least delayed when there are vast quantities of the
enzymes. Got that? Read more in the Scientific American.

Wait, there’s more, also in the Scientific American.