Many very certain lectures have been given on this subject.... - Beware certainty! Even though I am quite certain of the data with bariatric surgery, we are only beginning to understand HOW things work.
High fructose may not be the answer
Also, beware the non-surgeon's lack of data on the single case, short term success (also frequently brought out for lectures to convince you that it's just a willpower problem)
Yale's Rudd Center on regain risk
Unfortunately, the Rudd Center doesn't seem to get quoted on the relative success rate of surgery at 20 years (still an average of 50% excess weight off) versus their database of 800 patients (collected from around the world) at one year...
Ask your dietitian for long term data in their practice!