Thursday, August 28, 2014

Call For Abstracts: Canadian Obesity Summit, Toronto, April 28-May 2, 2015

COS2015 toronto callBuilding on the resounding success of Kananaskis, Montreal and Vancouver, the biennial Canadian Obesity Summit is now setting its sights on Toronto.

If you have a professional interest in obesity, it’s your #1 destination for learning, sharing and networking with experts from across Canada around the world.

In 2015, the Canadian Obesity Network (CON-RCO) and the Canadian Association of Bariatric Physicians and Surgeons (CABPS) are combining resources to hold their scientific meetings under one roof.

The 4th Canadian Obesity Summit (#COS2015) will provide the latest information on obesity research, prevention and management to scientists, health care practitioners, policy makers, partner organizations and industry stakeholders working to reduce the social, mental and physical burden of obesity on Canadians.

The COS 2015 program will include plenary presentations, original scientific oral and poster presentations, interactive workshops and a large exhibit hall. Most importantly, COS 2015 will provide ample opportunity for networking and knowledge exchange for anyone with a professional interest in this field.

Abstract submission is now open – click here

Key Dates

  • Abstract submission deadline: October 23, 2014
  • Notification of abstract review: January 8, 2014
  • Early registration deadline: March 5, 2015

For exhibitor and sponsorship information – click here

To join the Canadian Obesity Network – click here

I look forward to seeing you in Toronto next year!

@DrSharma
Montreal, QC

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Monday, August 25, 2014

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.

@DrSharma
Edmonton, AB

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Thursday, August 21, 2014

The Grizzly Truth About Healthy Obesity

While we continue to debatgrizzly-bear_566_600x450e the incidence and physiology of healthy obesity (i.e. adiposity without any evident health problems), there are ample examples of adiposity in the animal kingdom, where the accumulation of vast amounts of fat tissue are entirely compatible with good health.

One of these fascinating example is the grizzly bear, which accumulates enough fat to last all winter without any apparent ill-effects on its health – indeed, the accumulation of fat to a level that would be considered “morbidly obese” in humans in vital to its survival.

Thus, not only is “healthy” obesity possible in mammals, it may also be an important area of study to better understand healthy obesity (or lack of it) in humans.

Insights into healthy obesity comes from a fascinating study by Lynne Nelson and colleagues from Washington State University, in a paper published in Cell Metabolism.

The researchers studied metabolism in four adult female grizzly bears, trained to “voluntarily” allow blood samples to be drawn for this study (for a video on how exactly this was done click here).

Their study shows that as grizzly bears accumulate fat in preparation for hibernation, they become exquisitely insulin sensitive, only to switch to a state of insulin resistance as they enter hibernation. This process reverses as they emerge from hibernation months later.

While the paper describes in detail the metabolic and hormonal pathways involved in this modulation of insulin sensitivity (via PTEN/AKT signaling in adipose tissue, it suggests that it is the ability to maintain insulin sensitivity in the face of increased adipose tissue that allows these animals to remain metabolically healthy.

As readers may recall, this is akin to the finding in humans that healthy obese individuals also display high levels of insulin sensitivity compared to metabolically unhealthy obese individuals, who display the more typical insulin resistance.

While much of this ability to maintain insulin sensitivity in a state of adiposity may be genetic (as in the rare case of humans with PTEN haploinsufficiency) other factors that enhance insulin sensitivity (e.g. regular aerobic exercise) may also help prevent or alleviate the metabolic consequences of excess fat.

Other factors may well include the actual location of the expanded fat depots, with peripheral accumulation of subcutaneous fat being far less likely to cause metabolic problems (and perhaps even protect against) than visceral or ectopic fat.

Now I guess, we need a study to see how well healthy obese humans do in hibernation.

@DrSharma
Edmonton, AB

Hat tip to Susan Jelinski for pointing me to this paper

ResearchBlogging.orgNelson OL, Jansen HT, Galbreath E, Morgenstern K, Gehring JL, Rigano KS, Lee J, Gong J, Shaywitz AJ, Vella CA, Robbins CT, & Corbit KC (2014). Grizzly Bears Exhibit Augmented Insulin Sensitivity while Obese Prior to a Reversible Insulin Resistance during Hibernation. Cell metabolism, 20 (2), 376-82 PMID: 25100064

 

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Monday, August 18, 2014

Hormonal Responses to Food Intake Begin in Your Mouth

ChewOnThisLogoIn my current show at the 33rd Edmonton International Fringe Theatre Festival, I joke about the importance of chewing your food. This has classically been noted to be of importance to allow the enzymes in saliva to begin the process of digestion.

However, now a fascinating study by Yong Zhu and colleagues from Iowa State University, published in Physiology and Behaviour shows that chewing prompts hormonal changes that vary based on the composition of the food.

In their study, ten healthy males volunteers underwent a sham-feeding experiments (you chew but do not swallow your food) after an overnight fast with 3-min chewing of water, high-fat (nuts), high-carbohydrate (cereal) or high-protein (cheese) food provided in a randomized order (on four separate occasions).

While plasma glucose levels increased slightly and plasma lipids decreased slightly after all test foods, the high-carbohydrate food elicited significantly higher insulin, and the high-protein food resulted in higher ghrelin compared to other test sessions.

The authors attribute these changes in part to neuronal signals transmitted through the vagal nerve, which can for e.g. stimulate glucagon release, thereby explaining the observed increase in plasma glucose levels after all foods.

This study shows that short-term oral exposure to different foods can result in metabolic and hormonal changes that are partly dependent on diet composition.

If nothing else, this study points to the fact that chewing is not simply about mechanically preparing food for swallowing – it is far more a process that puts the organism into a nutritive state with distinct metabolic and hormonal changes.

Chew your food!

@DrSharma
Edmonton, AB

ResearchBlogging.orgZhu Y, Hsu WH, & Hollis JH (2014). Modified sham feeding of foods with different macronutrient compositions differentially influences cephalic change of insulin, ghrelin, and NMR-based metabolomic profiles. Physiology & behavior, 135, 135-42 PMID: 24952264

 

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Thursday, July 31, 2014

Low Adipocyte Formation Is Associated With Abdominal Obesity

sharma-obesity-adipocytes3One of the key concepts about the deposition of visceral and ectopic fat is the inability of “healthy” subcutaneous to readily expand to accommodate excess calories. This is why people with large fat cells and those with less or no subcutaneous fat (as in partial or complete lipodystrophy) display features of the metabolic syndrome.

In line with these observations, a study by Andre Tchernof and colleagues from the University of Laval, Quebec, in a paper published in ADIPOCYTE show that low adipogenic capacity of subcutaneous adipose tissue is associated with visceral obesity, visceral adipocyte hypertrophy, and a dysmetabolic state.

The researchers studied adipocytes and preadipocytes isolated from subcutaneous and visceral fat samples from 35 women undergoing gynecological surgery and assessed body fat distribution by CT as well as fasting plasma lipids and glycemia.

Using an in vitro differentiation assay, they found that lower adipogenic rates were strongly associated with increased visceral cell size and dyslipidemia.

In addition, When matched for BMI, women with low subcutaneous preadipocyte adipogenic rates had a higher visceral adipose tissue area, omental adipocyte hypertrophy, higher VLDL-lipid content and higher fasting glycemia.

All of these findings are in line with the notion that low subcutaneous preadipocyte differentiation capacity in vitro is associated with visceral obesity, visceral adipocyte hypertrophy, and a dysmetabolic state.

Once again, as regular readers should be aware, not all fat is equal.

@DrSharma
Edmonton, AB

ResearchBlogging.orgLessard J, Laforest S, Pelletier M, Leboeuf M, Blackburn L, & Tchernof A (2014). Low abdominal subcutaneous preadipocyte adipogenesis is associated with visceral obesity, visceral adipocyte hypertrophy, and a dysmetabolic state. Adipocyte, 3 (3), 197-205 PMID: 25068086

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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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