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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 a time-scale of decades, controlled experiments are prohibitively expensive or impossible. Instead, we have observational studies.

Taubes writes:

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.

Submitted by Bill Peterson