Cutting data won't make cutting weight easier

In my new book, I have a chapter on interpreting the statistics of obesity. Andrew Sullivan (link) recently pointed to a Nature article discussing an aspect of the controversy around these numbers. The bone of contention is the shape of the mortality curve. It has been thought that the curve is monotonic increasing, meaning that the higher your BMI, the higher the mortality rate. But survey data in the U.S. now show that the curve is probably U-shaped: mortality rates are high for both obese and thin people. Overweight (less than obese) people paradoxically seemed to live longer than those...