Genetics Influence Response of Body Weight to Gastric Bypass Surgery

Gastric bypass surgery is an increasingly utilized treatment option for severe obesity worldwide.  While this surgery can be very successful to result in substantial and sustained weight loss over the long term, individual results from person to person are highly variable.  A recent study suggests that a person's genetics may be the primary factor responsible for this variation.


The study, just published in the Journal of Endocrinology and Metabolism by Ida Hatoum and colleagues, examined the DNA of 848 patients undergoing gastric bypass surgery at the Massachusetts General Hospital.  Amongst these patients were 13 pairs of first degree relatives, none of whom were living together.  An additional 10 pairs of patients were identified who were living together but not related (thus allowing a comparison of the effect of environment on the efficacy of surgery). The remaining 794 people in the study were randomly paired for a non-genetic, non-environmentally connected comparison group.  

Interestingly, the study found that first degree relatives had a similar response to surgery, with an average of only 9% difference in the excess weight lost between members of each pair.  In contrast, there was a 26% difference in excess weight lost between cohabitating, unrelated individuals, which was no more similar than unrelated randomly paired individuals, who had a 25% difference in excess weight.

These results suggest that genetics have a strong influence on the effect of gastric bypass surgery on body weight.  Interestingly, they also suggest that the home environment does not have an influence on the efficacy of gastric bypass surgery.

We are certainly becoming increasingly aware of the strong genetic influence in obesity.  Dozens of genes which contribute to obesity risk have been identified so far, and this number continues to climb as our knowledge base grows.  It is therefore perhaps unsurprising to learn that genetics play a strong part in the response to bariatric (weight loss) surgery as well. 

The current study examines the influence of genetics on the lowest weight reached (called the 'nadir') after gastric bypass.  I would be very interested to know if genetics has an equally strong influence on the risk of weight regain after hitting the nadir weight postoperatively, as there is also quite a substantial variation in weight maintenance vs weight regain in the long run after bariatric surgery.  More study is needed in this area.

Although this study was too small to be able to identify the specific genetic contributors to weight loss success after gastric bypass surgery, larger scale studies could be undertaken to examine the entire human genome to try to identify the relevant genes.  It is likely that there are many genes involved here, and their interactions are likely to be extremely complex.  Discovery of new genetic mechanisms involved in the response to surgery may teach us something not only about surgery but about obesity in general, possibly leading us down the path to other discoveries that will assist us in non-surgical treatment of obesity as well.  

As for people currently contemplating gastric bypass surgery, this study is too small to make definitive conclusions, but if you have a first degree relative (parent, sibling, or child) who has had the surgery, the success they experienced may be predictive of your own.


Dr Sue Pedersen www.drsue.ca © 2011 drsuetalks@gmail.com

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Chatelaine Interview: The Latest News and Research in Obesity

A few months ago, I was asked to provide an overview of the undertakings at this year's Canadian Obesity Summit in Montreal, by James Fell, fitness columnist, certified strength and conditioning specialist, and the man behind Body For Wife.  

The complete article can be found at this link.  Below are some excerpts regarding elements of the Summit that I felt were important to highlight.  As some very controversial issues were raised and discussed, I thought I would post these items, and I'd really like to survey my readers as to their thoughts on these issues!  Please feel free to post a comment by clicking on the envelope icon at the bottom of this post - this is how we can get a good dialogue going, and stimulate change in our society! 


1. Genetics: “There are least 45 obesity-related genes that have been discovered and each one contributes 2-3kg to body weight. We don’t understand a lot about how they work; some create a different balance in hunger hormones and others cause fat storage. It’s not that some people are genetically fixed to be obese, but it can set the stage.”

Dr. Pedersen also mentioned how a woman who is obese while pregnant increases the prevalence of the child being obese through epigenetic changes that take place in utero.


2. Environment: “There was a lot at the conference about guiding Canadians to lead healthier lives. For example, should there be a junk food tax? Can we create programs to get Canadians to focus on weight loss and healthy eating and getting more exercise?”


3. Childhood obesity: “Eight percent of Canadian adolescents are obese, so how do we create good family-based programs to help them lose weight? These have to be focused on the parents because if they lose weight, then the kids lose weight by default.” 

Sue also had some interesting comments about adolescents and bariatic surgery. “Lap banding is favoured in kids [in extreme cases where it is deemed necessary] because it is the least invasive and is reversible. The Hospital for Sick Children in Toronto is the only place in Canada that is doing it right now. The decisions for bariatric surgery with children are very challenging.”


4. Adult obesity management: “There was a big focus on weight-loss surgery for people with Type 2 diabetes because the surgery can put it into remission. Having the surgery is done when the benefits of it outweigh the risks. Bariatric surgery can be the appropriate decision for a patient who has failed in all other attempts to lose weight.” Dr. Pedersen stated that such patients require psychological counseling as well, and that this is never a decision to be entered into lightly.

In regards to bariatric surgery, there is not enough funding so the wait list is about five years. Some provinces allow people to pay for it themselves, allowing lap banding for about $16-20 thousand for those who don’t want to wait.


Dr. Sue © 2011   www.drsue.ca     drsuetalks@gmail.com

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Should Adolescents Have Bariatric Surgery?

Obesity is a serious problem amongst all age groups, and we are seeing obesity affect younger individuals in higher numbers.  It is estimated that18% of American adolescents and 9% of Canadian adolescents are obese.   In adults, bariatric (weight loss) surgery is increasing recognized as an important treatment option for adults who suffer from severe or complicated obesity, in whom all other treatment options have been unsuccesful.  As such, the question is being raised as to whether adolescents with severe obesity should be considered for weight loss surgery.


This complex issue was discussed at the Canadian Obesity Summit last weekend in Montreal.  I had the pleasure of hearing several speakers from both the US and Canada, sharing their experiences on this issue.


Dr Evan Nadler, pediatric surgeon at the George Washington University School of Medicine & Health Sciences, discussed the various types of weight loss surgeries and the known data to date.   So far, preliminary evidence suggests that lap banding may be the most appropriate surgery to consider in this age group.  Early data suggests that the risks of gastric bypass surgery may be unacceptably high amongst teens, and there is little data regarding sleeve gastrectomy.  All three of these surgeries are being actively studied.


Dr Jill Hamilton, pediatric endocrinologist at the Hospital for Sick Children in Toronto presented the STOMP (SickKids Team Obesity Management Program), an innovative program which provides multidisciplinary support to adolescents with obesity, and for the appropriate candidate, bariatric surgery.  Five patients have been operated so far (with the first ones being done in October 2010), and this is the only pediatric Canadian site that is currently exploring this area.


Dr Beth Dettner, PhD and psychologist who works with the adolescents in the STOMP program, provided a poignant review of the psychological complexities of this population.  There are several challenges involved in selecting the appropriate teen for bariatric surgery: assessing for psychological conditions like depression, anxiety, and eating disorders, assessing family functioning and support for surgery, patients' and parents' understanding of the surgery and required diet and activity behaviours, the teen's coping skills, and their motivations for surgery are all key components.   


I found this to be an absolutely fascinating workshop, and I have a deep and renewed respect for the challenges that face adolescents with obesity, and their health care professionals as they work with these patients to find the most appropriate and successful treatment options.  Elements ranging from the high prevalence of binging and purging behaviours (as high as 30%), to the potential impact of gastric bypass surgery on accrual of peak bone mass, to the possibility of parental coercion to have the surgery, to the challenges of compliance with follow up, to specific motivations for desired weight loss (and the list goes on) all need special consideration in this population, and must be very carefully weighed against the potential weight, health, and psychosocial benefits that can result from successful bariatric surgery.


Dr. Sue © 2011   www.drsue.ca     drsuetalks@gmail.com

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FDA Gives Thumbs Up to Broader Lap Banding Indications While Research Gives Thumbs Down to Long Term Outcomes

For some individuals, despite intensive and longstanding attempts at shedding pounds and exhausting every possible lifestyle intervention or medical therapy, weight loss remains elusive.  In some cases, weight loss surgery (called 'bariatric' surgery) may be the most appropriate option.  Bariatric surgery has typically been reserved for the most extreme cases, but recently, the American FDA has lowered the Body Mass Index (BMI) requirements for eligibility to undergo laparascopic adjustable gastric banding ('lap band') surgery.


As blogged previously, bariatric surgery has traditionally been reserved for the most serious cases of obesity, defined as a Body Mass Index of 40 or greater, or, a BMI of ≥ 35 with one or more serious complication of obesity, such as diabetes, obstructive sleep apnea, or high blood pressure (you can calculate your own BMI in the right hand column here).  However, because of the impressive success that bariatric surgery can have to result in weight loss and reduce complications of obesity, the FDA has lowered the required BMI for a patient with a serious complication of obesity to 30 for the lap band procedure.

However, as blogged previously, recent study suggests that lap banding may actually have a poor long term outcome.   It is interesting that the FDA seems to be embracing the most extreme of obesity treatments by expanding indications for bariatric surgery, in a form that may be associated with poor long term outcomes, while simultaneously (and in some experts' opinions, perhaps stringently) rejecting a lineup of three potential new weight loss medications in the last year.


For Canadians, the BMI criteria for bariatric surgery remain unchanged.  If we were to follow our US counterparts with a broadening of the BMI criteria, it would make little practical difference in any case, as the average wait time for bariatric surgery across Canada is over half a decade.  In addition, in light of recent study suggesting that lap banding may have a poor long term outcome, other types of bariatric surgery (such as gastric bypass) may be more appropriate to consider, though these other forms of surgery have a significant risk of complications as well, and long term outcomes of these procedures are not yet well known. 


Dr. Sue © 2011   www.drsue.ca     drsuetalks@gmail.com

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Bariatric Surgery - Patient Guide to Endocrine and Nutritional Management

As blogged previously, bariatric (weight loss) surgery is a treatment options for people with severe obesity that has proven to be resistant to treatment with more traditional and conservative measures. The treatment does not end with the surgery itself, however - the story is far more complex than that.

As beautifully summarized in the Patient Guide to Endocrine and Nutritional Management after Bariatric Surgery in the Journal of Clinical Endocrinology and Metabolism (a free download!), there are several aspects which require close attention and follow up in order to minimize the chance of weight regain after surgery, to minimize the risk of developing a complication of bariatric surgery, and to ensure that complications of obesity are well managed postoperatively.

To decrease the chance of weight regain after surgery, a lot of the preventive work actually has to happen before the surgery is even done. It must be recognized, as with any 'diet', that the lifestyle change being made has to be a permanent one. This is not about eating smaller portions or altering food choices for a short period of time - this is forever. It is also absolutely critical that the relationship with food is thoroughly explored and managed well before the surgery takes place. There are many contributing factors to overeating, many of them emotional: eating in sadness, in joy, to comfort, to alleviate stress, even to service a true addiction to food. People who have not had help in dealing with these aspects of their weight struggles, or who have not worked through these issues prior to surgery, are not appropriate candidates for bariatric surgery, as they stand a high risk of weight regain postoperatively if those habits and coping mechanisms are not managed beforehand.

The risk of nutritional deficiencies is very real after bariatric surgery, particularly after gastric bypass surgery (pictured above), which involves a re-routing of the small intestine such that about 1.5 meters of small intestine is no longer exposed to food and the enzymes required to digest it. Patients who undergo gastric bypass surgery are at risk of life threatening complications if they do not adhere to their supplement regimen, which for most patients includes a specific multivitamin, calcium, vitamin B12, vitamin D, and often iron. An individual who is committed to having gastric bypass surgery must be equally committed to taking supplementation for the rest of their lives. Protein malnutrition is a potentially severe complication of any type of bariatric surgery due to decreased intake; it is essential to follow the protein consumption recommendations provided by the bariatric program's dietician (usually at least 90 grams of protein intake per day).

Because bariatric surgery often has a profound beneficial impact on several obesity-related complications such as diabetes, high blood pressure, obstructive sleep apnea, cholesterol, and osteoarthritis (to name a few), it is important to have physicians involved both pre- and post-operatively who can help to manage changes in medications and treatment approach that are often necessary.

While bariatric surgery is a very appropriate treatment option for some people, it must always be remembered that bariatric surgery is not a quick fix or a cure; it is the exchange of one set of medical issues for another (though usually in a positive direction), and it is most certainly a permanent lifestyle alteration.

Dr Sue Pedersen www.drsue.ca © 2010 drsuetalks@gmail.com

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The Psychology of Weight Loss Surgery

For an individual who is being considered for bariatric (weight loss) surgery for management of their obesity, it is becoming increasingly clear just how pivotal psychological issues are in the management before, during, and after the procedure. While there are many psychological benefits to bariatric surgery, there are also significant psychological risk that must be taken into careful consideration.

At the American Diabetes Association meeting in Orlando, FL, last week, I attended a lecture by Dr Lucy Faulkonbridge, Assistant Professor of Psychology at the University of Pennsylvania, who reviewed this topic for her audience.

There are many great things to be said about the psychological benefits of bariatric surgery. Bariatric surgery has been found to reduce depression and anxiety amongst individuals undergoing these procedures. The majority report improvement in body image, psychosocial functioning, and quality of life. Sexual function is also usually improved, as a consequence of many factors, including increased interest and improved mobility.

Having said the above, there are also potential negative consequences, some of which are absolutely devastating. While depression usually improves with weight loss, symptoms of depression can return, particularly in those who had significant depression prior to surgery. Importantly, while one study found that the risk of death was reduced by 40% at 7 years after gastric bypass surgery, they also found an increased risk of death from suicide and accidental deaths in this population.

Although bariatric surgery is typically very successful in achieving weight loss, the results can vary greatly from person to person. According to the landmark Swedish Obese Subjects' Study , as many as 10% of gastric bypass and 25% of gastric banding patients are unable to maintain even a five percent weight reduction with surgery. (We do appreciate a 5% body weight reduction, as 5% weight loss in an obese individual decreases the risk of developing serious obesity-related complications such as heart disease, diabetes, and cancer.) Interestingly, the success of weight loss surgery seems to depend in part on psychological issues. While a background of psychological issues in a general sense is not predictive of degree of weight loss, active symptoms of depression or a tendency towards binge eating prior to surgery tends to result in smaller weight losses after surgery.

Although the literature in this area is somewhat conflicting, DrFaulkonbridge postulated that while distress related to psychological illness may be an impediment to the success of bariatric surgery, distress related to extreme obesity may be a predictor of greater success, as this distress should improve with weight loss. The key is to determine what the source (or sources) of distress is/are prior to surgery, such that these issues can be addressed and dealt with prior to surgery, in order to optimize the medical and psychological outcomes of the procedure.

The psychology behind post operative exercise routines may play a part, too. In patients who have had gastric banding, those who did not increase their activity level after surgery are much more likely to have weight regain than those who do become more active post operatively. There is also some data to suggest that some patients may actually engage in less physical activity after the surgery, despite having shed pounds and most often enjoying increased mobility. Having an exercise program established prior to surgery is an important component to maintaining long term success with these permanent lifestyle changes as well.

Follow up patterns with the surgeon was also identified as being associated with weight loss success. While only 40% of patients return for their annual visits with their surgeon after their operation, it is these patients who seem to have the best weight loss success. The relationship between weight loss success and compliance with follow up is likely multifactorial.

It is clear that psychological issues must be taken into very serious consideration prior to, during, and after bariatric surgery. Key points to highlight include:

1. Thorough psychological evaluation and counseling before bariatric surgery is paramount. This should ideally take place in the form of screening questionnaires, as well as counseling and support from mental health care professionals. It is important that active mental health issues are dealt with as well as possible prior to surgery, to provide the greatest chance of success. It is noted that some people may not be appropriate candidates for bariatric surgery if their psychological issues are not stable or well managed.

Ideally, this process should take place as part of a team approach to preparation for bariatric surgery, including help from dieticians, nurses, physicians, and occupational therapists. Psychological support is also crucially important towards preparation for the permanent lifestyle change that defines bariatric surgery (very small portion sizes, alteration in food preferences, and a permanent change in one's relationship with food).

2. Psychological support and access to mental health professionals through and following the bariatric procedure, both short term and long term. The needs of the individual patient will vary greatly - it is the availability, and experience of health care professionals in dealing with the issues that may arise, which are key.

3. Support from friends and family throughout the process. A solid support network provides outlets to deal with emotional issues that may arise. It is important that a patient's loved ones are accepting and understanding of the motivations behind bariatric surgery, and are equally prepared to both endure the trials, and celebrate the tribulations, that may lay along the path towards successful weight loss.

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Provincial Variation in Accessibility to Bariatric Surgery

At the Inaugural Diabetes Surgery Summit in Montreal last week, it became apparent that there is significant provincial variation in accessibility to weight loss (bariatric) surgery. As Dr. Nicolas Christou of McGill University pointed out, in Canada in 2008, the number of bariatric surgeries performed in each province was as follows:

- Nova Scotia: 28
- New Brunswick: 17
- Quebec: 802
- Ontario: 579
- Saskatchewan: 23
- Alberta: 272
- BC: 160

The reasons for the provincial variation are complex. One interesting phenomenon that was brought up was that in Ontario, patients had previously been funded by the provincial health care system to have bariatric procedures done in the United States - this was a situation that was unique to Ontarians, as no other province provided funding to do this. Due to the enormous expense of sending patients over the border and the potential savings of having these surgeries done at home, the Ontario government provided funding to build access to the service in their home province, to the tune of many millions of dollars in cost savings. As other provinces never had the situation where patients were funded to go south to have surgery, the same financial pressure does not exist to bring the procedure home.

In the mix of the numbers above, other factors have to of course be considered, including population density and surgical expertise available in each province (though with increased provincial funding for bariatric surgery, the surgical expertise would be likely to follow).

Even in provinces with the most accessibility to surgery, however, there is still an enormous shortage of availability country wide, with an estimated fifteen year backlog of patients who would be appropriate for, and benefit from, the surgery.

What can we do? Get out there and talk about it.

Dr. Sue © 2010 www.drsue.ca drsuetalks@gmail.com

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