Bariatric Surgery – More Than Expected

Bariatric surgery doesn’t only cause dramatic weight loss—the procedure itself has profound metabolic effects, according to studies published in the September issue of Gastroenterology.

Two types of bariatric surgery are most effective therapies for sustained weight loss in obese patients. In Roux-en-Y gastric bypass (RYGB), a gastric pouch drains into the mid-jejunum and pancreaticobiliary flow is diverted to the distal jejunum. So, ingested food bypasses most of the stomach, the entire duodenum, and a short portion of jejunum. Alternatively, in vertical sleeve gastrectomy (VSG), 80% of the stomach is removed but intestinal anatomy is unaltered (see figure).

RYGB and VSG surgeries

Patients that undergo these procedures usually lose more than 60% of excess body weight. Furthermore, more than 80% with type 2 diabetes acquire normal fasting glucose concentrations and levels of insulin sensitivity, often before any substantial weight loss occurs. Researchers compared the effects of these surgeries, as well as dieting, in rats.

Margaret Stefater and colleagues found that plasma levels of lipids decrease greatly after bariatric surgery, which might explain why this procedure reduces the risk for cardiovascular disorders. The reduction in lipid resulted from the surgery itself, rather than changes in eating habits of the rats; the drop in plasma levels of lipid after VSG was weight-independent and  caused by attenuated postprandial triglyceride production in the intestine. High plasma levels of lipid cause atherosclerosis, particularly in obese patients; Stefater et al. propose understanding the mechanisms by which VSG lowers lipid levels could lead to new therapies for atherosclerotic disease.

But is RYGB or VSG a better method for weight loss? Adam Chambers et al. compared the effects of each surgery on metabolic effects in obese rats, and found that both produce weight loss-dependent increases in overall insulin sensitivity. However, they also produce weight loss-independent increases in hepatic insulin sensitivity and release, as well as levels of glucagon-like peptide-1 (GLP)-1. GLP-1 is an intestinal hormone released in response to nutrients that regulates glucose levels; Chambers et al. found it was required for the beneficial effects of each procedure on levels of glucose after eating. The increases observed in GLP-1 did not result from reduced body weight or caloric intake—rats that lost weight on a control diet had no changes in GLP-1or insulin release.

So these surgical procedure themselves, beyond the resulting weight loss, have beneficial effects for obese patients. Chambers et al. conclude that RYGB and VSG produce similar outcomes in terms of effects on food intake, body weight, and resolution of type 2 diabetes. They propose that because VSG is a technically simpler operation and requires less recovery time than RYGB, and because VSG is not associated with the malabsorption of micronutrients, it could be the best choice for many patients.

In an accompanying editorial, Rexford Ahima and Ahlam Sabri state that although the results from Stefater et al. showed that VSG decreased postprandial triglyceride levels, there are no known mechanisms that regulate intestinal triglyceride secretion—it will be important to determine whether VSG alters intestinal triglyceride secretion through gut hormones. Further studies are needed to determine whether VSG and RYGB differentially influence intestinal transit and neural and hormonal mechanisms.

More Information on Bariatric Surgery:

Read the articles online. These articles have an accompanying podcast.

Stefater MA, Sandoval DA, Chambers AP, et al. Sleeve gastrectomy in rats improves postprandial lipid clearance by reducing intestinal triglyceride secretion. Gastroenterology 2011;141:939-949.e4.

Chambers AP, Jessen L, Ryan KK, et al. Weight-independent changes in blood glucose homeostasis after gastric bypass or vertical sleeve gastrectomy in rats. Gastroenterology 2011;141:950–958.

Read the accompanying editorial:
Ahima RS, Sabri A. Bariatric Surgery: Metabolic benefits beyond weight loss. Gastroenterology 2011;141:793–795.

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About Kristine Novak, PhD, Science Editor

Dr. Kristine Novak is the science editor for Gastroenterology and Clinical Gastroenterology and Hepatology, both published by the American Gastroenterological Association. She has worked as an editor at biomedical research journals and as a science writer for more than 12 years, covering advances in gastroenterology, hepatology, cancer, immunology, biotechnology, molecular genetics, and clinical trials. She has a PhD in cell biology and an interest in all areas of medical research.
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3 Responses to Bariatric Surgery – More Than Expected

  1. carlos poron says:

    thank`s for this simplyficated information, greetings from guatemala; we recently begun our gastroenterology program, I`ll advice my collegues about this topic, thank`s again

  2. I am a bariatric patient that underwent RYGB in November of 2004. I did see a dramatic, sudden weight loss that has been pretty much sustained over time. In terms of weight loss, most would deem my surgery a success. However, in terms of overall health, there are so many subsequent difficulties that have raised concerns and appear to be related to the surgery, such as: indigestion, esophageal spasms, chronic vomiting that persisted for more than 3 years, several bouts of H. Pylori infection, an emergency cholecystectomy, continued treatment for GERD, prolonged malabsorption, tested positive for 1 marker of celiac disease (treating as gluten intolerant), uncontrollable bowels & frequent incontinence, excruciating flatulence, and chronic gastritis. I would like to find out how to become involved with current research in this area. I feel that my personal experience with RYGB would make an excellent case-study and I am eager to know how to rectify current symptoms and prevent future degradation of health. Please let me know if you have any ideas or contact information that is helpful. Thanks so much!

  3. Leanderjuel says:

    Many thanks for this detail on your experience after having Bariatric Surgery. While all people and situations are unique, there is historical reason to suspect that your reality is only one of many or not a stand-alone situation…so, any patient who is considering this approach and others like yourself who have gone through it …need to be fully aware of the post surgery challenges so that unnecessary surgery is avoided or those like yourself might join forces to be of one voice to better educate the public. I mean, you are to be commended for wanting to be part of the solution by participating in a research study. Especially when, intuitively, it stands to reason that when any major alteration is done to the in-tact stomach, there would be subsequent reactions and/or adverse events to further challenge the body. So, did you seek a second opinion and was your surgeon openly transparent while cautioning on the potential or risk of these outcomes before the surgery? If not, keep in mind how there is an inherent conflict of interest.

    This article and your illuminating reply caught my eye because I recently read where our local non-profit hospital chain has added their first bariatric surgeon to the staff for our coastal-rural community. Needless to say, a rural community where jobs are scarce [affects food/lifestyle choices], the healthier nutritional education is sparse and there are enough unhealthy and overweight people on Medicaid or Medicare to justify the demographic reason. While I mean no slight, and hope you are soon successful in regaining the healthier status of balance and appropriately functioning metabolism, I am of the opinion there is little sound or holistic reason to treat the issues of weight [gain] with structurally invasive and as you now confirm, ‘life-altering’ surgery. Again, my sincere appreciation for your personal details. More than you may realize, it is essential for any prospective bariatric candidate to see such ‘been there’ honesty.

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