Wednesday, July 23, 2014

In Memorium: Albert (Mickey) J Stunkard

Stunkard twinsAs I spend my days at the 9th Canadian Obesity Network’s Summer Bootcamp for young trainees from Canada and around the world, I was saddened to learn of the passing of Mickey Stunkard, clearly one of the biggest names in obesity research – at a healthy age of 92.

With well over 500 publications to his name, Mickey is perhaps best known for his twin studies showing that the body weight of adopted identical twins reared apart resembles each other and that of their biological parents rather than the weight of their adoptive parents.

This work helped establish the basis for much of the genetic work on obesity that followed, clearly showing that differences in body weight between two individuals are much more accounted for by their difference in genetics than by differences in their “lifestyles”.

These findings were often misused in “nature vs. nurture” debates, an issue that serious scientists have long laid to rest in light of our current understanding that the two cannot be discussed separately, simply because genes and lifestyle interact on virtually every level – from molecules, to cells, to behaviours.

Here is what one obituary had to say about Mickey:

“He surveyed obesity treatment studies in the late ’50s and found that the nation’s diet programs could claim only a 2 percent success rate. He was an early advocate for the use of bariatric surgery to induce weight loss. He also published the first modern account of binge eating in obese individuals.”

I have had to pleasure to often hear him speak at conferences.

He will be dearly remembered.

@DrSharma
Kananaskis, AB

 

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Friday, July 18, 2014

Birth Control And Obesity

sharma-obesity-birth-control-pillAlthough obesity is a well-recognised factor for female infertility, the vast majority of women with excess weight are probably more interested in effective birth control.

That this is not as simple as it seems is evident from an article by Sheila Mody and Michelle Han from the University of California, San Diego, published in Clinical Obstetrics and Gynecaology.

The paper succinctly reviews a wide range of issues related to birth control and obesity.

To begin with, the authors points out that unintended pregnancies in obese women are often a problem simply because obese women are far less likely to use effective contraception than non-obese women. This non-use may in part be attributable to fear of weight gain, when most studies show that modern hormonal contraception is associated with almost no weight gain. The exception appears to be depot-medroxyprogesterone (DMPA), which may cause about 5 lb weight gain in the first year of use.

As for efficacy, the data show that unintended pregnancy rates among overweight women using oral contraceptives are similar or slightly higher than that among nonoverweight women. The reasons for these higher rates are not exactly clear.

Fortunately, the efficacy of intrauterine devices (IUD) appear no different between obese and non-obese women although the insertion of an IUD maybe more difficult in obese women because of poor visualization of the cervix and limited assessment of uterine position (a problem that can often be solved with the help of an ultrasound).

The paper also discusses the suitability of the vaginal vaginal contraceptive ring, which has been hypothesized to offer higher hormone levels for obese women than oral contraceptives because the hormones are absorbed directly into the vaginal mucosa and do not go through the first- pass liver metabolism.

Finally, the paper discusses issues around contraception for women who have undergone bariatric surgery (who have a particularly high rate of unintended pregnancies) as well as best practices for emergency contraception.

This is clearly information that all clinicians who counsel obese women should be aware of.

@DrSharma
Edmonton, AB

ResearchBlogging.orgMody SK, & Han M (2014). Obesity and Contraception. Clinical obstetrics and gynecology PMID: 25029338

 

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Tuesday, July 15, 2014

The Molecular Biology of Food And Mood

sharma-obesity-brainThe neuroendocrine systems that control ingestive behaviour are intimately linked to the parts of the brain that control mood.

Thus, it is increasingly evident that factors that affect energy homeostasis (diet and exercise) can have profound effects on mood while changes in mood can have significant effects on appetite and energy homeostasis.

But this relationship is far from straightforward – rather, it appears to be rather complex.

Readers interested in an overview of how these two systems interact in the brain may find a recent review by Chen Liu from the University of Texas Southwestern Medical Center, Dallas, published in Cell Metabolism of interest.

The authors review our current understanding of how mood and food are linked with particular attention to appetite, ingestive behaviour and energy homeostasis.

The article also touches on the effects of pharmacological and surgical treatments for obesity on mood.

Clearly clinicians need to be aware of the close links between these systems and draw on our current understanding of both in their counselling of patients presenting with weight gain and/or depression.

@DrSharma
Edmonton, AB

ResearchBlogging.orgLiu C, Lee S, & Elmquist JK (2014). Circuits Controlling Energy Balance and Mood: Inherently Intertwined or Just Complicated Intersections? Cell metabolism, 19 (6), 902-909 PMID: 24630814

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Thursday, July 10, 2014

Can Germs In Your Drinking Water Help Prevent Obesity?

sharma-obesity-tap-water1In my show I joke about how I intend to import water from the river Ganges as a new obesity treatment that I will appropriately name “RunFast”.

Jokes aside, a study by Zhongyi Chen and colleagues, published in the Journal of Clinical Investigation, shows that treating mice with genetically modified bugs delivered through their drinking water can protect them from becoming obese even when fed a high-fat diet.

To be exact, the researchers used a strain of e coli bacteria genetically engineered to produce N-acylphosphatidylethanolamines (NAPEs), which are precursors to the N-acylethanolamide (NAE) family of lipids, normally synthesized in the small intestine in response to feeding and known to reduce food intake.

As their study shows, administration of these modified bacteria in drinking water for 8 weeks dramatically lowered food intake, weight gain, body fat, insulin resistance and liver fat in mice on a high-fat diet.

These “protective effects” lasted for at least 4 weeks after removal of these bacteria from the drinking water.

In another set of experiments the researchers also showed that this strain of bacteria reduced weight gain in a genetic model of mouse obesity.

Contrary to what one may believe, this study neither supports nor refutes the idea that gut bacteria may be partly responsible for the obesity epidemic.

Rather, the study primarily shows that bacteria may be used as a delivery system for “therapeutic doses” of molecules to the intestines – in this case, resulting in the modification of appetite and metabolism.

I would not be surprised if the therapeutic use of bacteria (genetically modified or not) opens up a whole new dimension of therapeutics – not just for obesity.

@DrSharma
Edmonton, AB

ResearchBlogging.orgChen Z, Guo L, Zhang Y, L Walzem R, Pendergast JS, Printz RL, Morris LC, Matafonova E, Stien X, Kang L, Coulon D, McGuinness OP, Niswender KD, & Davies SS (2014). Incorporation of therapeutically modified bacteria into gut microbiota inhibits obesity. The Journal of clinical investigation PMID: 24960158

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Tuesday, July 8, 2014

Does BMI Underestimate Adiposity in Kids?

sharma-obesity-kids-scale2Regular readers are well aware of my reservations regarding the use of BMI as a diagnostic parameter in clinical practice. After all, while BMI may tell us how big someone is, it certainly is not a good measure of how sick someone is.

But to be honest, BMI was never intended as a measure of disease – it was (at best) introduced as a surrogate measure of adiposity (fatness).

Nevertheless, supporters of BMI continue to argue that it is still a good measure of fatness and as such should remain part of standard assessment – even in kids.

Now, a paper by Javed and colleagues, published in Pediatric Obesity, examines how well BMI performs as a means to identify obesity as defined by body fatness in children and adolescents.

The authors conducted a systematic review and meta-analysis of 37 studies in over 53,000 participants assessing the diagnostic performance of BMI to detect adiposity in children up to 18 years.

While the commonly used BMI cut-offs for obesity showed showed a high specificity (0.93) to detect high adiposity, the sensitivity was much lower (0.73) – particularly in boys.

This means that kids who exceed the current BMI cut-offs are indeed very likely to have fatter bodies (for what it’s worth).

On the other hand, relying on BMI cut-offs alone will miss as many as 25% of kids whose body fat percentage exceeds current definitions of adiposity.

Thus, assuming that bod fatness or adiposity is indeed a clinically useful measure of health, the use of BMI alone will ‘underdiagnose’ adiposity in a significant proportion of kids (especially boys) who may well be at risk from excess fat.

A word of caution about fatness is certainly in order – as in adults, much depends on exactly where the fat is located (abdominal or ectopic vs. subcutaneous) and other factors (e.g. cell size, inflammation, insulin sensitivity, etc.).

Thus, even if BMI was a perfect measure of body fat, it would probably still require further examinations and tests to determine exactly whether or not this “extra” fat poses a health risk.

As in adults, a clinical staging system similar to the Edmonton Obesity Staging System may be a fat better indicator of determining which kids may need to worry about their body fat and which don’t.

@DrSharma
Edmonton, AB

Hat tip to Kristi Adamo for pointing me to this study

ResearchBlogging.orgJaved A, Jumean M, Murad MH, Okorodudu D, Kumar S, Somers VK, Sochor O, & Lopez-Jimenez F (2014). Diagnostic performance of body mass index to identify obesity as defined by body adiposity in children and adolescents: a systematic review and meta-analysis. Pediatric obesity PMID: 24961794

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In The News

Diabetics in most need of bariatric surgery, university study finds

Oct. 18, 2013 – Ottawa Citizen: "Encouraging more men to consider bariatric surgery is also important, since it's the best treatment and can stop diabetic patients from needing insulin, said Dr. Arya Sharma, chair in obesity research and management at the University of Alberta." Read article

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