Vagal Nerve Blockade for Weight Loss?

As severe obesity has proven so difficult to treat, much study is underway to try to find innovative treatment options.

The vagus nerve is thought to play an important role in the feeling of fullness (called 'satiety') and metabolism, so the question has arisen as to whether blocking this nerve could help to treat obesity.
An interesting study recently reported in the Journal of the American Medical Association (JAMA) was published, evaluating whether intermittent blockade of the vagus nerve would be effective to induce weight loss.

This study was a randomized, controlled trial of 239 patients with a Body Mass Index (BMI) between 35-45, where an electrical device was implanted to intermittently block the vagal nerve in half of the patients, and the other half had a 'sham' surgery (meaning they went through the implantation procedure, but the device was not hooked up to the vagus nerve).  All patients received lifestyle counseling.

They found that at 1 year, the vagal blockade patients lost a little more weight (3.2%) than the control group, but the vagal blockade group also had a higher risk of serious adverse events (8.6% vs none in the control group). Interestingly, the control group, with lifestyle counseling only, lost 6% of their body weight (compared to 9.2% in the vagal blockade group), showing that lifestyle counseling alone (plus a possible placebo effect of the sham surgery) can result in substantial weight loss.

So, based on this study, intermittent vagal nerve blockade doesn't seem like a promising option - weight loss benefits are minimal, and the rate of serious adverse events is concerning.

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Bariatric Surgery - More Long Term, High Quality Data Needed

Based on the available evidence, bariatric (obesity) surgery is effective to improve upon complications medical conditions related to obesity (such as type 2 diabetes and sleep apnea) and helpful for weight loss.  However, most of this data is based on shorter term results, and there is a concern regarding gaps in high-quality knowledge as to the benefits and risks of bariatric surgery over the long term.

In a recent literature review by Puzziferri and colleagues in Journal of the American Medical Association,  the current status of long term high quality data in bariatric surgery research was assessed.  They examined the literature to see just how much high quality longer term data is out there (defined as studies of 2 years or more, with follow up data on at least 80% of patients by the 2 year mark).

They found that only 29 studies total (less than 3% of studies identified) had 80% or more of patients followed up past the 2 year mark (7,971 patients total).  On analysis of available data in these studies, they found that the average excess weight loss was 66% for gastric bypass surgery, vs 45% for gastric band.  Type 2 diabetes remission rates (based on 6 studies) were 67% for gastric bypass, vs 29% for gastric band.  Remission of hypertension (high blood pressure, based on 3 studies) was 38% for gastric bypass and 17% for gastric banding. There wasn't enough data to analyze these parameters for sleeve gastrectomy.  No study had data past 5 years.  Concerningly, only half of the studies reported on complications at least 2 years after surgery.

So, while the existing high quality long term data is encouraging, we are still lacking in quantity of good quality data (clinical trials with low long term dropout rates) to have a thorough understanding of long term effects of bariatric surgery.  While we do have encouraging observational studies to guide us on longer term benefits vs risks of bariatric surgery (encouraging particularly for gastric bypass surgery and sleeve gastrectomy), randomized controlled clinical trials ideally need to be done and patients followed long term (with less dropouts) to have a more comprehensive understanding of long term effects.

The above being said - as discussed in a recent study by Courcoulas and colleagues, and as I can certainly attest to from my own research experiences - this is a tall order to fill.

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A Different Kind of STAMPEDE

Obesity (bariatric) surgery has become accepted as an option for the treatment of type 2 diabetes by most diabetes guidelines around the world. The data on which these recommendations are based are from shorter studies, from weeks to months to up to 2 years. 

Now, in a landmark randomized controlled trial published in the New England Journal of Medicine, 3 year data shows us that the benefit of bariatric surgery to diabetes control is sustained out to at least 3 years.

The study, called the STAMPEDE study, randomized 150 people with type 2 diabetes, to receive either intensive medical treatment of diabetes alone (with a goal A1C of 6.0%), vs medical treatment plus gastric bypass surgery, vs medical treatment plus sleeve gastrectomy.

The study clearly shows that gastric bypass surgery and sleeve gastrectomy are superior to intensive medical therapy alone, to have control of type 2 diabetes at 3 years. Thirty-eight percent of patients who had gastric bypass surgery had tight control at 3 years, compared to 24% after sleeve gastrectomy, compared to only 5% receiving medical treatment alone. (The difference between the gastric bypass and sleeve groups was not statistically significant.)

With the above being said, I do take issue to how this study was structured, in that the goals for control of diabetes were too tight. We no longer recommend an A1C of 6.0% as a goal, as another landmark study (the ACCORD study) showed that control this tight was associated with an increased risk of death. It would be interesting to know how the numbers would have panned out if the commonly accepted A1C target of 7.0% was used instead.

However, the point of the article remains that gastric bypass and sleeve gastrectomy results in control of type 2 diabetes in significantly more patients than medical treatment alone. There is no doubt that Bariatric surgery is an important tool in our toolbox of diabetes therapy in the 21st century.

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Do Hormones Play A Role in Weight Loss Failure After Bariatric Surgery?

Obesity surgery is currently the most effective treatment available for severe obesity.  While the smaller stomach reservoirs that are created by these surgeries play a major role in the weight loss seen, it is becoming increasingly evident that there are many other contributors at work, one of which is thought to be alterations in various hormone levels after surgery.

I was asked to write a review article discussing what we know about hormone changes in relation to weight loss failure and weight regain after bariatric surgery, which was recently published in the journal Gastroenterology Research and Practice.  In the article, I review eight of the key hormones thought to be involved in the weight changes after bariatric surgery (from GLP-1 to PYY to oxyntomodulin, bile acids, and others), as well as what we know about the hormone changes that occur after the four main types of bariatric surgery (gastric banding, sleeve gastrectomy, Roux-en-Y gastric bypass, and biliopancreatic diversion).

In summarizing what we know about hormonal associations with weight loss failure and weight regain after bariatric surgery, there was painfully little to discuss - there is unfortunately very little data in this area.

What became poignantly clear to me from compiling this review is that more research is desperately needed to help us understand how hormones may contribute to weight loss failure or regain after obesity surgery.  As I noted in the article,

In the future, with a better understanding

of this complex arena, assessment of hormone status

could potentially be helpful in understanding the hormonal

contributors to a patient’s postoperative weight loss failure

or recidivism, potentially aiding the clinician in utilizing

appropriate targeted hormone therapy to help them achieve

successful or sustained weight loss.

This is probably not a wish I should expect to see fulfilled anytime soon - after all, pinpointing hormonal predictors of weight regain after 'regular' dietary-induced weight loss has proven evasive as well.  However, with a dedicated body of bariatric researchers worldwide, I hope that we will learn more about this important area with time. 

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Could Obesity Surgery Increase the Risk of Colon Cancer?

As for any medical treatment or surgery, the decision to undergo bariatric surgery requires that the benefits and risks are carefully evaluated by the patient and the health care team.  Amongst the list of benefits, several studies have suggested that bariatric surgery decreases the risk of cancer amongst women.   Now, a new study suggests that the risk of colorectal cancer may actually be increased after obesity surgery.

The study was an evaluation of the population database in Sweden, looking at the colon cancer incidence rates amongst men and women who had obesity surgery (gastric bypass, gastric banding, and an older procedure called vertical banded gastroplasty), compared to patients with obesity who did not have bariatric surgery.  They found that amongst those who had had bariatric surgery, the risk of colon cancer was 60% higher than those who hadn't had surgery (though the absolute numbers were fairly low - 70 out of 15,095 patients, or 0.46% of patients who had obesity surgery developed colon cancer).  Ten years after bariatric surgery, the risk of having colon cancer was double compared to people with obesity who hadn't had bariatric surgery.

These results need to be taken with a grain of salt, as there are a number of limitations to this database analysis - for example, other risk factors associated with colon cancer such as smoking, diabetes, family history etc were not available (the interested reader can read more about this here).  The study does seem to contradict the overall protective effect that bariatric surgery is thought to have on cancer risk (for women, at least) - but then again, most previous studies have not followed up patients for as long as this one, and colon cancer is known to be a very slow growing tumor.

Following gastric bypass surgery, it has been suggested that the lining of the intestine may change (called 'mucosal hyperproliferation'), and an increase in a pro-tumor chemical has been found (a cytokine called 'macrophage migration inhibitory factor'), though other tumor inducing chemicals (such as TNF alpha and interleukin 6) have been shown to decrease after bariatric surgery.  The population of intestinal bacteria change after surgery as well, and there is still much we don't know about the effects of these changes (though there appear to be metabolic benefits of these post-surgery bacterial changes).

So where does this leave us?  Well, there are still many questions to be answered about the long term efffects of bariatric surgery, which only time will teach us.  In the meantime, we must continue to carefully weigh the benefits and risks of obesity surgery, and for patients who have had bariatric surgery, colon cancer screening and surveillance should be undertaken.

@drsuepedersen

www.drsue.ca © 2013

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Excess Skin After Bariatric Surgery

On the second day of the Canadian Obesity Summit, I had the honor of being asked to act as a judge for a number of excellent research presentations during the poster session.  First, a heartfelt congratulations to all of the presenters - I was truly impressed by all of your efforts and studies, and I enjoyed each of our stimulating conversations!

A study that really struck a chord with me, and which I feel is really important to share, was a study looking at the impact of excess skin on physical activity in women who have had bariatric surgery.  The reason for doing this study is that over 70% of patients who have bariatric (obesity) surgery are left with excess skin that interferes with physical and social functioning. The research, conducted by A Baillot and colleagues at the University of Sherbrooke in Quebec, administered questionnaires to 26 women who had had bariatric (obesity) surgery at least 2 years prior, asking women about how their excess skin impacted them physically, psychologically, and socially.

They found that 77% of patients reported that their excess skin was making mobility during physical activity difficult, and that almost half were avoiding physical activity because of their excess skin.  What really hurt my heart was that when these women were asked why the excess skin caused them to avoid physical activity, the most common reason cited was that they were concerned about people staring at them (other reasons were hygiene concerns, weightiness of the excess skin, and a feeling of 'sloshing' of the skin).

My take home message from this study is that the likely development of excess skin after obesity surgery is something that needs to be discussed in detail with patients prior to having surgery, such that they are prepared for the physical, psychological, and social challenges that they may perceive or encounter.

And, as always, it is my hope that with education of our society, that any obesity related stigma that may exist out there will continue to decrease until it disappears entirely.  I was asked a lot at the summit as to why I blog - this reason would be amongst the highest.

Dr Sue Pedersen www.drsue.ca © 2013 

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Nutritional Support After Bariatric Surgery

Today, I would like to kowtow to my friend and colleague Dr Priya Manjoo, endocrinologist at the University of Victoria, who gave a fantastic talk about nutritional support of the bariatric patient at the Canadian Obesity Summit. 

I'll highlight a few of the key points here: 

1.  Prior to obesity surgery, many patients are already often deficient in nutrients; for example, one study showed that 65% of patients were deficient in vitamin D before surgery, and 27% were deficient in iron.  Therefore, it is imperative that these levels be checked and corrected before surgery is undertaken. 

2.   Following obesity surgery, there are a number of reasons why nutritional deficiencies can occur,  including insufficient intake due to dietary restrictions and food intolerances, anatomical causes due to changes made in the intestinal anatomy, and a disconnect between the timing of release of digestive enzymes and entry of food into the intestine. 

3.  Dr Manjoo then went through a fabulous review of the various vitamins and nutrients that we need to be on the watch for after bariatric surgery.  Adequate protein intake, and monitoring and supplementation (depending on the type of surgery) of calcium, vitamin D, iron, vitamin B12, folate, thiamine, zinc, copper, and selenium are all things that we need to think about.

Finally, as previously blogged, she pointed us towards the 2013 American Bariatric Guidelines for some guidance on this complex topic. 

Thanks Priya for a fabulous session!

Dr Sue Pedersen www.drsue.ca © 2013 

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