obesity market report and/or article on obesity drug failure

I am looking for a report or an article of the drugs for obesity, an analysis of the potential growth, new drugs in development, size of the market It is also helpful to get a scientific background on obesity and how the drugs work in the body like xenical etc. Recently there have been a lot of failures of drugs in obesity from Orexigen, Arena Pharma and Vivus. Describe the reasons of the failures, that is why it is important to get the scientific background.