I don't know about Dean Ornish, but Gary Taubes is a journalist, as far as I know, not a nutrition expert. Maybe his research on his books turned him into an expert, not sure.
I have to admit the Good Calories, Bad Calories book seemed a bit unstructured to me. In the end it was just listing a load of studies in favor of his thesis. It left me wondering if perhaps he only selected those that supported his claims.
The problem with researching diets is probably the long term aspect of it. How do you make people stick to a diet you randomly assign to them for 20 years? It also has an ethical component, because you might assign unhealthy diets.
Gary Taubes is not just a journalist. He is a science journalist with a background in physics. This is an important distinction because he has the necessary training to correctly interpret scientific studies. That's what his book is about: it's a huge meta-study that explores the history and the current state of nutrition science. And his ultimate finding is that mainstream nutrition science is wrong and it's carbs that should be avoided, not fats.
But ultimately why believe him instead of some other scientist? Because his book is thicker? I also noticed that he had a bit of a tummy when I saw a YouTube video of him.
I've read another thick book advocating plant based diets and metaanalyzing lots of studies, The China Study. GC,BC is a bit thicker, though.
I think I already gave you the answer: Taubes' book is a comprehensive meta-study that examines the merits and pitfalls of most prominent studies in the field of nutrition science. This allowed him to draw broader conclusions than any specific study.
Really though, you just have to read it, apply your critical thinking skills to it, and make up your own mind.
I have to admit the Good Calories, Bad Calories book seemed a bit unstructured to me. In the end it was just listing a load of studies in favor of his thesis. It left me wondering if perhaps he only selected those that supported his claims.
The problem with researching diets is probably the long term aspect of it. How do you make people stick to a diet you randomly assign to them for 20 years? It also has an ethical component, because you might assign unhealthy diets.