Robert Lustig is a research doctor. he works at UCSF (it's where my PhD in Biophysics is from), and sees patients there- highly obese, atypical patients. He promotes a particular position about metabolism and health. However - and this is the key thing - he has NOT published data which is convincing to reasonable scientists to support his position. At UCSF, he's generally considered a bit of a quack (personal comments from a number of professional scientists who work there).
Here is a list of Lustig's publications. http://scholar.google.com/scholar?hl=en&as_sdt=0,5&q=author:...
I, working with grad students at UCSF and elsewhere, have picked apart the materials and methods of his studies and found numerous statistical errors which make us doubt the validity of his conclusions. I won't claim that we have evidence he is being fraudful- it's more likely just an example of poor scientific behavior.
I'll give Lustig credit for one thing. Sugar- the Bitter Truth is one of the finest examples of manipulative sophistry I've ever seen. After seeing that I realized that most scientists are doing an absurdly poor job manipulating the public.