[pitchups]

Not exactly a control group, but among the group of 22 patients who did not follow the diet, 13 or 62% had some sort of adverse event (stroke/heart-attack etc), compared with just 1 out of the group of 177 (0.6%) who did follow the diet. That seems to be pretty compelling evidence that the approach is effective.

[nordsieck]

One immediate issue is that conscientiousness, e.g. the ability to maintain a difficult diet for an extensive period of time, is quite correlated with longevity.

This is a very commonly known effect, which makes me more than a bit suspicious of this particular study.

This is also why a control group with random assignment is necessary, particularly in the social sciences. There are simply too many confounding factors to make epidemiology useful in basically any way.

[rgbrenner]

It's not. For all we know, those that were unable to follow the diet were those who had the worst cases and/or least healthy diets.