A long life

I saw this talk:
http://www.ted.com/talks/dan_buettner_how_to_live_to_be_100.html
which, unlike Aubrey De Grey, claims that human life is limited to about 90. Well, Aubrey De Grey doesn't say that it's not currently limited: just that with research we could work to change the limits.

He talks about many things, but the most telling point was, I think, that little section about the stress response and the inflammatory state. Inflammation is directly linked to ageing, and connects stress to ageing. Things such as friendship help reduce stress; not individual points of stress, perhaps, but the background level of stress a person experiences, which, as Dan Buettner explains for exercise, is far more important than individual events, certainly in the context of a whole life.

The good diets and the lack of over-eating play into this again: obesity is directly linked with the inflammatory state. This might not be as well recognised as for stress, but is an assertion supported by a mountain of evidence of its own. The more overweight a person becomes, the more his body suffers from a systemic, chronic inflammatory state.

All the points he made boil down to effects on this one condition: the inflammatory state of the body. It is quite possible that the much-hyped longevity of starvation, in which animals fed on diets 20% of the normal, or other meagre diets, works via a lack inflammation, since the immune system is a hugely energy-demanding part of the body, consuming thousands of calories when fighting infection. Starvation, in the sterile setting of a laboratory animal house, will force the animal to shut the inessential immune system, and therefore forgo the inflammatory signals that lead to ageing.

Hints and tips, gleaned by statistical surveys of the elderly, might help a little with improving our life expectancy, but their primary purpose must always be to illuminate underlying mechanisms. There is no point to knowing an extra little habit can net you an average of 2 days' extra life if it is the one-hundredth habit you must incorporate into your life. We need these rules because once we have worked out, using complex statistical techniques, the common features to all long lives, they will guide us to a deeper understanding of the problem.
Many rules will take us back to old wives' tales and traditional Chinese medicine, in which the good rules are obscured by a vast catalogue of pointless commandments produced quite possibly with the best of intentions but with the effect of hiding truth, not revealing it. Once we have linked enough long lives to deduce sufficient rules, we must turn ourselves to deducing the links between the rules: a second level of linkage and deduction.