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How Does Bariatric Surgery Work?

sharma-obesity-gastric_bypass_roux-en-y3Regular readers will be well aware of the fact that bariatric (unfortunately, often referred to as “weight-loss surgery”) is currently the most effective treatment for severe obesity.

However, exactly why and how surgery works remains unclear. Earlier concepts of surgery working either because it creates a mechanical restriction to food intake and/or reduces caloric load due to malabsorption are not borne out by newer studies.

Rather, it seems that complex neurohormonal changes together with often profound changes in ingestive behaviour act together to account for the resulting weight loss (and more importantly) for the long-term weight-loss maintenance.

Just how many factors interact in specific and unspecific ways to lower body weight is now discussed in a review paper by Timothy Sweeney and John Morton, from Stanford University, in a paper published in Clinical Gastroenterology.

As the authors discuss, there is a complex interaction between a wide range of factors including several hormones (leptin, ghrelin, adiponectin, glucagon-like peptide 1 (GLP-1), peptide YY, and glucagon), bile acid changes in the gut and the serum, and changes to the gut microbiome.

The most profound changes in these systems are seen with the roux-en-Y gastric bypass, which induces large and distinctive changes in most measured fat and gut hormones, including early and sustained increase in GLP-1, possible through intestinal bile acid signaling. This may well explain why this operation appears to be the most effective and durable procedure.

Clearly, hope remains that by better understanding the exact mechanisms through which surgery (which will only ever be available to a vanishingly small minority of people with excess weight) works, we will identify mechanisms and targets for desperately needed pharmacological treatments.

Edmonton, AB


  1. I had my surgury in 87 I am an RN and there was the data available for me 4 yrs ago I developed a stricture and have to go for endoscopics q6months for dilation I went down to 100 lb I am now with the tx 160 lbs its a challenge I know the surguries for the kost are much more less complex its the long trem effects iam an active 76 yr old

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  2. On the 19th of this month. My surgeon at the Royal Alexandra performed Vertical sleeve gastrectomy on me. Pre-Operatively I lost 75 lbs of weight through hard work, journalling, attending seminars, participating in a support group, walking, and working with a fabulous team of Obesity professionals including a Psychologist and a Psychiatrist at the Royal Alex.

    I am thankful for the WeighWise program (old name) as I learned more than the average bear! For that, I owe my life. The surgery is a tool or an aide to help me to maintain or better yet manage my weight and food intake.

    I know that this is a permanent new lifestyle and that year pre-op helped establish new habits and ways of thinking. Post-Op as I awoke to some fairly intense pain, I thought what the heck did I do, but now a week after and on a liquid diet as my stomach heals, I already understand my new stomach – we have a new relationship. He talks – I listen, I ask and he confirms. A few sips here and a few there…”are you full…ah yes I feel that you are!”, “Okay, we can wait 5, 10, 15 minutes to finish my soup no problem…why rush it ?” I am excited for my new Chapter…at 54, I would love to have a quality 30-40 more years!….I now have a greater probability of achieving that!

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