I thought I’d throw in a quick answer to the first/original poster here. In terms of the story of ‘high metabolism = die early’ thing, this appears to be true ACROSS species. This means, as a general rule of thumb, anxious animals like rats live shorter lives than slower animals like turtles. So, typically calculated as a per body weight basis, increased metabolic rates lower average lifespan. BUT, this is not necessarily true WITHIN a species; so humans with healthy highish metabolisms (not HYPERthyroid per se) DO NOT live shorter lives than humans with clinically or sub clinically hypo metabolisms (as judged by temperature or thyroid hormones levels). I think this community is finding the opposite is often true.
The other issues is Calorie Restricted animals, which shows that IF you begin CR (or Intermittent Fasting) in young animals, they live longer than those who eat at liberty. But this has several large caveats:
First, the average lifespan is reduced in animals upon being placed in captivity and the increase in lifespan the average in the population gets back after being calorie restricted ALMOST gets back the length lost due to captivity.
Second, several other restrictions have comparable effects to CALORIE restriction, including METHIONINE (a sulfurous amino acid) and glucose restriction (carb restriction). In all restrictions, the animals grow up to be quite small (meaning small bone frame and less muscle mass). However, a recent paper showed that the Met restriction only helped longevity due to a decreased Met/Glycine ratio. Rats eating at liberty PLUS a glycine supplement gave the same longevity increase as Met restriction (and same as overall CR), but resulted in body size equivalent to the rats eating at liberty without restriction. Glycine is found naturally in collagen/gelatin; methionine is high in muscle meat, eggs, and dairy.
http://www.fasebj.org/cgi/content/meeting_abstract/25/1_MeetingAbstracts/528.2
Third, the lifespan benefits of CR or any restriction ONLY benefits animals when the restriction begins as YOUNG animals. If the CR begins a while after this young age, the animals live shorter lives than those fed at liberty. I think Matt Stone also had mentioned this somewhere in a past (now erased) blog post. I have never seen a study that posted this information in the abstract, but I have seen this evident in the results pages of several studies. I think this is showing that young animals essentially ‘grow into’ the food they eat; but a body that has ‘grown into’ calorically dense foods, will become severally HYPOmetabolic when switching to a lower caloric intake and die of disease. My hunch, though I haven’t seen this ever studied, would be that the restriction will be deadly to an adult animal whether the restriction is via eating a lower amount of the same calorically dense food or simply switching to paleo/natural foods and eating lower total calories. I also surmise that the larger the body size and higher the metabolic rate of the adult, the more drastic the health deterioration will be upon restricting. Sound familiar anyone?
