I just wanted to say real interesting thread, I am so thankful you guys are fleshing this issue out for people like myself who can follow along on the sidelines but are not actually knowledgeable enough to partake in the investigation (yet) 
In regards to the low carb & high fat VS moderate to high carb & low to moderate fat approaches, to those following the latter, how do you respond to the DukeNukem school of thought that carbs[insulin] = aging? Acknowledging my pro-paleo stance, Dr. Harris (PaNu) states the kernel of his theory is "Insulin is a phylogenetically old hormone. It is a biological messenger that in excess, is metabolically saying the following to your tissue and organs: "Go ahead and store energy, mature, reproduce and die."". I know this is a rather crude non-detail considering statement, but it seems most people here accept a similar crude/simple theory as to why CR works: hunkering down & survival mode, shift focus away from reproduction and instead on maintenance and repair for when food is more abundant, etc. Now I understand that the high carb & low fat is found in many long lived populations, so in that respect it is almost a sure thing in terms of longevity promotion, but I feel like we have the ability to go better than simply what works for X population and going directly to the science. And I think this is what is happening for example with PUFA. It doesn't really matter any more if X long lived population had a high PUFA consumption, or many studies showing benefit, the big picture is emerging that it would be advised to keep PUFA < 10%
I guess I thought we had the carb thing nailed, that basically the less insulin you have flow through your veins throughout your life, ceteris paribus, the better?
Kismet gave you a pretty good and toughtful answer, as usual, and I simply want to add a little bit of what I've learned in my own parcour.
I used to believe that epidemiology did not mean squat (mislead by people who denies it because many epidemiological studies goes againsnt their hypothesis), and I was and still am largely & often speculating more than I should. Someone who I greatly respect here told me that it's about time that we understand that epidemiology on clinical end point (mortality, aging, pathology, etc) trumps any speculation we can have about a phenomenom. And indeed, i'm reading a very good book on critical appraisal of studies, and they say that epidemiology can indeed be use to prove causation, if you've got enough good quality studies showing the same result, because many things will never be able to be test in an experimental setting - so it's either epidemiology or speculation, you choose.
But I think you should trust more the fact that many population made it to a very high age and in good health on a high-carbs diet... it's a good hints, and even if it doens't show that carbs are healthy, it's probably show that they are not detrimental per se.
As for the PUFAs, that's why i'm trying to go with the epidemiology right now and think that PUFA can't be that bad, even will all the speculation we can make about it. After all, they keep lowering CHD incidence in many prospective cohort studies.
And as for the carbs=aging, a pelo-diet is probably usually higher in protein than a high-carb diet, and protein will stimulate many aging factor, such as IGF-1, leucine will stimulate mTOR-pathway, and probably other that i'm not aware of, such as the methionine issu that i've never took the time to dig.
A paleo diet is pro-anabolic, as demonstrated many time by peoples (myself included) who can shed fat and pack muscle while on it very efficiently. As I understand it, too much anabolism is pro aging.
As kismet said, I really don't think you can bring aging down to carbs and insulin. The real big picture is much, much more complicated than what we can understand by now.
Edited by oehaut, 29 April 2010 - 12:58 PM.
