Define 'stress', especially for these animals. Wouldn't you think that living in a laboratory cage is 'stressful'? If that's the daily baseline, I can't see how 'stress' can be a catchall explanation for even borderline cases. Administering anesthesia is a form of surgery. Even if they're related, would you want to say that death during surgery is a form of aging?

More importantly, deaths are just one of the variables being measured. The diet seems to improve quality of life, not just raw quantity. That's reason enough to be interested in these findings.

Furthermore, the author of this blog seems to doubt the role of Science in publishing these findings. The money they make has no bearing on the results. Other scientists, doing closely related work, reviewed the work in excruciating detail (read the footnotes, not the press releases) and found its clear scientific value. Sure, blame the media for the headlines. But the work, as a status report on the field, is very encouraging.

Because the monkeys weren't being underfed and it's a straw man to suggest they were. Tibetan monks get by on much less food than we do and they will still kick our asses anytime.

You're assuming that a monkey that eats 20% less than a monkey that's given the choice to eat as much as it wants necessarily isn't underfed? Maybe. But without some other research that I've missed, that really begs the question.

I think anyone living in a western country has enough data to realize that people eating a western diet tend to be overfed, so the comparison between westerners and Tibetan monks has little to do with monkeys.

In the caloric restriction experiments, the nutritional density of the food the animals are fed is almost always increased. Fewer calories, same levels of protein, nutrients, etc. It's not just a matter of 'less'.

From what I've read, humans on caloric restriction diets have to design their diets carefully, to increase the nutritional density of their own food supply. (E.g. http://www.calorierestriction.org/Getting_started)

Do you really think your casual pondering of the matter has revealed an insight not obvious to the experienced, professional scientists who designed and are now running this large scale, multi-decade experiment?

It beggars belief they have not considered, and painstakingly controlled for, such factors.