| In this case, a "well established method" simply means common-place methodology, not necessarily a robust scientific protocol. The problem is the humans. We are not reliable witnesses, even of our own pasts, and unless we are following very strict diets, most of us essentially follow a mostly random walk with our food intake across a narrow range of food groups (even caloric intake can be wildly inconsistent over time). I've met enough people who completely underestimate their consumption of desserts, e.g., that they mentally reduce the occurrence of such events in their personal historical narratives. That alone could put many from both low-carb vegans and low-carb meat eaters into the high-carb category. Which is the point, the worst failure of this methodology is that there is no evidence that human memory, regarding food consumption, provides an accurate measure over long periods of time. If you cannot establish the trustworthiness of the most basic tool of your methodology, then almost by definition it's meaningless. The error in self reporting could be high enough such that the true classification of 80% of the low carb group is actually high carb. Or the vegan group could be nearly half high-carb, etc. Without a thorough vetting of the accuracy of the instrumentation used in the research (FFQ in this case), we cannot know the margins of error. But we have apriori reasons for believing the accuracy to be significantly high. Adding more people to the group doesn't increase the accuracy in this case, it only increases the volume of the noise. Is the True Low Carb ratio of each group 10% or 90%? Who knows. If we can't validate the accuracy of the tools, it makes the results essentially a random choice between the possible conclusions. It means they haven't disproven the null hypothesis. Which is why I favor some form of sequestration of smaller populations of similar genetic makeup (multiple groups for each type of diet), etc. But that is mostly impractical. |