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Does Dietary Weight Loss Predict Surgical Outcomes?

sharma-obesity-bariatric-surgery21Currently there is no way to reliably predict whether or not a given patient will do well with bariatric surgery or not.

Although most patients do, a substantial number struggle with post-surgical complications or simply fail to lose adequate amounts of weight.

Now a study by Mirna Azar and colleagues from the University of Ottawa, published in OBESITY, suggests that weight loss over six weeks on a low-calorie liquid diet as part of a behavioural weight-loss program may predict subsequent weight loss with laparoscopic Roux-en-Y gastric bypass (RYGB).

The observational studied looked at data from over 200 patients, who underwent RYGB following a previous dietary and behavioural intervention.

Overall there did appear to be a relationship between weight loss on six weeks of the low-calorie diet and the weight loss response at 26 weeks post surgery.

However, despite statistical significance, this relationship hardly meets the criteria of a “clinically predictive” test and probably performs dismally on an ROC curve in terms of both sensitivity and specificity.

Nevertheless, the fact that there was any relationship at all is intriguing and one can only speculate as to why this may be the case.

I can indeed think of a number of reasons ranging from genetic differences (susceptibly to weight loss) to differences in behaviour such as adherence and compliance with the dietary recommendations that may explain this relationship.

Overall however, predicting who does well with surgery and who does not continues to be a mystery even if many clinicians often kid themselves when they think they can tell.

This is unfortunate, as identifying patients most likely to do well (or perhaps more importantly, identifying those who will not) remains an important challenge in the field of bariatric surgery.

Edmonton, AB


  1. That’s quite interesting and fits with my experience. I had to wait 4 months between my meeting with the surgeon and my RNY surgery. I put myself on a 900 calorie a day diet (I looked up the nutritional stats on Optifast and tried to basically match them with real food). I lost 98 lbs before the surgery and went on to lose another 166 lbs after from 387 at surgeons meeting to 123 lbs lowest weight. I’m struggling with some regain but am still far below what they told me to expect.

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  2. Great study and blog. My question is, how patients fair when they go through a medical program and gain weight and still go to surgery. What really makes a truly bad candidate for surgery? As you pointed out Arya, thats what we need to know. Red lights are those with active drug and alcohol dependency causing, and active signficant mental health conditions such psychosis. Other than that, we have very few guidelines not to proceed with surgery. It is a very opinionated field with little accurate data. I look forward to some work on this, hmmmmmm, Maybe I should do it. Arghhhhhh More work. 🙂 Sean

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    • Yes, the Red Lights you mention are the obvious contraindications, but beyond that we have little to go on

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