I finally finished Why We Get Fat today. It wasn't that high on my priority list since I'd already read Good Calories, Bad Calories.
There's actually quite a bit of new material in the book - about 1/3 of it is new. Some of it is things like the AtoZ study that was published since Good Calories, Bad Calories came out. However, I think a big part of it was a difference in what Taubes saw as the purpose of the book.
The main purpose of Good Calories, Bad Calories was to get medical researchers to accept that fat phobia didn't have a good scientific basis, point out that we didn't really know for sure what the cause of the obesity epidemic is, and encourage them to do some solid, unbiased, experimental research.
Why We Get Fat is more of an advocacy book: even though we don't have scientific proof that carbohydrates, via insulin, are the main cause of obesity today, Taubes feels that sufficient evidence points in this direction that he feels comfortable advocating a low carb diet in this book.
Since he's going beyond what has been strictly scientifically proven, though, he does go out on a limb on some things. For example, he starts to blame "refined" carbohydrate more than other carbohydrates, even thought the scientific evidence doesn't really support such a differentiation. Also, he makes claims that fructose in particular is problematic in ways that I don't think is supported by the evidence.
Still, it's much less heavy reading than Good Calories, Bad Calories, even if it can hardly be classified as light, so it will likely actually get read by more people.
