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Why nutrition Is so confusing
by Gary Taubes, New York Times, 8 February 2014

Taubes reports that in 1960, fewer than 13 percent of Americans were obese and only 1 percent were diagnosed as diabetic. At the time, fewer than 1100 articles on obesity or diabetes appeared in the indexed medical literature. In the years since then, the obesity percentage has increased by a factor of 3, and diabetes percentage by a factor of 7. But more than 600,000 research articles on these conditions have now appeared in the literature.

For perverse "association is not causation" example, one might suggest that publishing articles on obesity causes people to be overweight! Actually, Taubes's essay takes a more serious stab at the problem. Because heart disease and diabetes unfold on such long time-scales, controlled experiments can be prohibitively expensive if not impossible. Instead, we have observational studies, that can only suggest how various dietary factors might affect health outcomes.

Taubes writes that:

The associations that emerge from these studies used to be known as “hypothesis-generating data,” based on the fact that an association tells us only that two things changed together in time, not that one caused the other. So associations generate hypotheses of causality that then have to be tested. But this hypothesis-generating caveat has been dropped over the years as researchers studying nutrition have decided that this is the best they can do.

Thus,

...we have a field of sort-of-science in which hypotheses are treated as facts because they’re too hard or expensive to test, and there are so many hypotheses that what journalists like to call “leading authorities” disagree with one another daily.

He cites Karl Popper: “the method of science as the method of bold conjectures and ingenious and severe attempts to refute them.” In this formulation, Taubes concludes research on nutrition is out of balance. It is good at generating conjectures, but in need of more vigorous efforts at refuting them.

Submitted by Bill Peterson