Citation for a study...

I'm riting a paper and doing a presentation for a class of mine. I need the source (or at least any reputable source) for a statistic I've read about. I could swear I saw it in one of the WLS books I own, but can't seem to find it.

The statistic is something like: ~80% of morbidly obese people succeed long term with RNY (maybe just general WLS) while only ~2-5% succeed with even the best diet and exercise programs.

I found it on a couple different websites but I know the actual study, or at least an actual book that cites the study beter is out there. I just need some help finding it. Someone must know something about it!

Thanks in advance for the help!

 There are some results about long term weight loss with RNY in this post:

http://www.meltingmama.net/wls/2010/10/stomaphyx-results.html

I don't have a diet link.

Here's a study on the outcome of RNY but it doesn't compare it to those that do not have WLS.

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1421028/