Here are some explanations to a question that was posted on obesityhelp.com website at:

http://www.obesityhelp.com/forums/DS/4108700/This-very-well-could-be-a-stupid-question/

The Swedish Obese subject group of studies (SOS studies) have been looking at a lot of the questions that are raised.

1-The relationship between diet-exercise, and weight loss surgery. It is the study that demonstrated that weight loss surgical procedures were far more superior than the conventional diet and exercise plans. Their original data offered a relationship between the non surgical method and the RNY gastric bypass, VBG, and banding procedures. The long term outcomes (15 year data are plotted. What is of significance is that the control (the non surgical group) had no sustained weight loss.

2- The follow up questions was in reference to if there are any mortality benefit to weight loss surgical procedures.  This is a question that only recently been answered, since it takes time to see if patients that have had weight loss surgery leave longer or not. The published data in NEJM in 2007 by SOS group answered this same specific question.

This data (graph on the left) demonstrated that in a 16 year period the cumulative mortality rate was better (lower) in the weight loss surgical limb than that of the non surgical limb. 

This was the very first time that a large enough study showed that not only a patient looses weight, but also leaves longer after weight loss surgery. 

This does not specify the differences between different weight loss surgical procedures. It also does not distinguish between the long term outcomes of the different procedures. 

Ara Keshishian, MD, FACS, FASMBS

The graphs are from http://content.nejm.org/cgi/content/full/357/8/741