Wednesday, June 18, 2014

4th Canadian Obesity student Meeting (COSM 2014)

Uwaterloo_sealOver the next three days, I will be in Waterloo, Ontario, attending the 4th biennial Canadian Obesity Student Meeting (COSM 2014), a rather unique capacity building event organised by the Canadian Obesity Network’s Students and New Professionals (CON-SNP).

CON-SNP consist of an extensive network within CON, comprising of over 1000 trainees organised in about 30 chapters at universities and colleges across Canada.

Students and trainees in this network come from a wide range of backgrounds and span faculties and research interests as diverse as molecular genetics and public health, kinesiology and bariatric surgery, education and marketing, or energy metabolism and ingestive behaviour.

Over the past eight years, since the 1st COSM was hosted by laval university in Quebec, these meetings have been attended by over 600 students, most presenting their original research work, often for the first time to an audience of peers.

Indeed, it is the peer-led nature of this meeting that makes it so unique. COSM is entirely organised by CON-SNP – the students select the site, book the venues, review the abstracts, design the program, chair the sessions, and lead the discussions.

Although a few senior faculty are invited, they are largely observers, at best participating in discussions and giving the odd plenary lecture. But 85% of the program is delivered by the trainees themselves.

Apart from the sheer pleasure of sharing in the excitement of the participants, it has been particularly rewarding to follow the careers of many of the trainees who attended the first COSMs – many now themselves hold faculty positions and have trainees of their own.

As my readers are well aware, I regularly attend professional meetings around the world – none match the excitement and intensity of COSM.

I look forward to another succesful meeting as we continue to build the next generation of Canadian obesity researchers, health professionals and policy makers.

You can follow live tweets from this meeting at #COSM2014

@DrSharma
Waterloo, Ontario

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Tuesday, June 10, 2014

Surgical Weight Loss Reduces Sympathetic Nerve Activity

sharma-obesity-verticalsleevegastrectomyOK, to some folks this may not be all that new a finding – after all the drop in sympathetic nerve activity with weight loss is one of the main reasons that weight loss reduces blood pressure. Unfortunately, it is also one of the main reasons that metabolic rate is reduces with weight loss.

For anyone, who wonders what happens to sympathetic activity following surgical weight loss, a study by Gino Seravalle and colleagues from the University of Milan, Italy, published in HYPERTENSION has some answers.

Their study in patients undergoing sleeve gastrectomy, studied before as well as six and twelve months post surgery not only shows a respectable drop in blood pressure and heart rate but also a marked and persistent decrease in leptin levels and in muscle sympathetic activity as measured by microneurography. They also showed a significant improvement in baroreceptor sensitivity.

Together these data certainly provide strong evidence that massive weight loss (in this case 9 BMI units) induced by sleeve gastrectomy, triggers profound sympathoinhibitory effects, associated with a stable and significant reduction in plasma leptin levels.

Obviously, much of this can be achieved with non-surgical weight loss, except that finding subjects who lose that amount of weight and keep it off for 12 months without surgery is far more difficult (but not impossible) and therefore much harder to study.

@DrSharma
Edmonton, AB

Hat tip to Bill Colmers for pointing me to this study.

ResearchBlogging.orgSeravalle G, Colombo M, Perego P, Giardini V, Volpe M, Dell’Oro R, Mancia G, & Grassi G (2014). Long-Term Sympathoinhibitory Effects of Surgically Induced Weight Loss in Severe Obese Patients. Hypertension PMID: 24866140

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Monday, February 17, 2014

Why Hunger Lets You Smell Through Doors

sharma-obesity-olfactionWhy does hunger make our noses more sensitive to the smell of food?

This riveting scientific enigma has now been solved thanks to the tireless work of Edgar Soria-Gómez and Luigi Bellocchio (together with a distinguished team of European colleagues), the results of which are now revealed in Nature Neuroscience.

As casual observers may not be all that surprised to learn, it turns out that the mechanisms involves the exact same system implicated in “the munchies” (Yes, those munchies).

Using pharmacological and genetic experiments in mice, the researchers showed that stimulation of cannabinoid type-1 receptors in the main olfactory bulb (the smell centre) promotes the animals’ ability to smell food when hungry (and eat it).

The fact that hunger draws our focus to smelling out foods of course makes a lot of sense – now at least we know how this works.

How else would you make it back to camp just in time for dinner?

@DrSharma
Edmonton, AB

ResearchBlogging.orgSoria-Gómez E, Bellocchio L, Reguero L, Lepousez G, Martin C, Bendahmane M, Ruehle S, Remmers F, Desprez T, Matias I, Wiesner T, Cannich A, Nissant A, Wadleigh A, Pape HC, Chiarlone AP, Quarta C, Verrier D, Vincent P, Massa F, Lutz B, Guzmán M, Gurden H, Ferreira G, Lledo PM, Grandes P, & Marsicano G (2014). The endocannabinoid system controls food intake via olfactory processes. Nature neuroscience PMID: 24509429

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Monday, July 30, 2012

Alcohol, Sleep Deprivation and TV Watching Drive Overeating

Regular readers are well aware that I am more interested in the ‘whys’ of why people eat than in the ‘whats’ of what they eat.

Now a paper by Colin Chapman and colleagues from Upsalla University, Sweden, published in the American Journal of Nutrition, looks at the key lifestyle drivers of overeating, with a particular focus on TV watching, sleep deprivation and alcohol consumption as studied in controlled laboratory settings with healthy volunteers.

Their search of the literature yielded 8 television studies, 5 sleep studies, and 10 alcohol studies.

All three of these factors had significant effects on food intake in the laboratory setting with alcohol having the strongest effect, followed by sleep deprivation and TV viewing.

With regards to the possible mechanisms on how these behaviours affect food intake, the authors have the following to offer:

Alcohol consumption:

“Alcohol is known to induce alterations in circulating ghrelin, a peptide implicated in food reward. In addition, alcohol affects g-aminobutyric acid and opioid systems. The alteration of g-aminobutyric acid signaling in reward centers of the brain stimulates appetite, and opioid signaling has been implicated in regulating the orosensory reward components of eating. These pharmacologic findings are consistent with human studies that showed a greater increase in hunger during the early phase of a test meal after an alcohol preload compared with an energymatched carbohydrate preload. This mimics the pattern of response shown when the palatability of food is enhanced through flavor manipulation.”

Sleep Deprivation:

“There is similar evidence that links sleep deprivation to an increase in the hedonic value of food. Sleep loss causes a constellation of metabolic and endocrine changes, including an increase in circulating ghrelin. Interestingly, recent studies on sleep deprivation have found that it increases overall brain response to palatable food image. In particular, short sleep increased activation in brain areas involved in reward processing, such as the putamen, nucleus accumbens, thalamus, insula, and anterior cingulate cortex. This strongly suggests that sleep deprivation, like alcohol, leads to deregulation of reward system activation in response to food.”

TV Watching:

“Several of the studies included in the meta-analysis found that the effect of television viewing on food intake was most pronounced with high-calorie foods, which suggests that television viewing alters the saliency of food reward. Epidemiologic studies have shown a similar trend, in that those who watch more television tend to snack more while watching and to consume more energy-dense snacks. Additional evidence suggests that watching images of palatable food increases plasma ghrelin concentrations.”

The implications of all of this, when seen in the context of habitual reinforcement and perpetuation of such behaviours are worth noting:

“With regard to the lifestyle factors analyzed, all three, when experienced habitually, should strengthen memory traces that trigger reward expectancy to food cues: that is, when presented with rewarding food or food cues, people who often suffer from sleep deprivation or who often watch television or drink alcohol while eating are more likely to experience a greater reward response as a result. In addition, both alcohol and television likely become their own conditioned cues for those who consume food in conjunction with these factors.”

The authors are optimistic that addressing these factors early on (especially in kids and young adults) may be important measures to reduce the risk of obesity. Thus, they cite evidence that curbing alcohol consumption, increasing sleep time and reducing TV viewing may all lead to decreased accumulation of body fat.

Based on these findings I guess it is time to lay off the night cap, turn off the TV and go to bed.

AMS
Edmonton, Alberta

p.s. Hat tip to Carlene for pointing me to this article.

p.p.s. Maintaining this blog costs both time and money – if you have enjoyed these posts, please consider making a small donation to the upkeep of this site by visiting my website by clicking here.

ResearchBlogging.orgChapman CD, Benedict C, Brooks SJ, & Schiöth HB (2012). Lifestyle determinants of the drive to eat: a meta-analysis. The American journal of clinical nutrition PMID: 22836029

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Wednesday, March 28, 2012

ISORAM Day 2: Eating With Your Brain, Taste Alterations, Glucose Transport, and Dietary Fibre

Day 2 of the 2nd International School on Obesity Research and Management (ISORAM) was kicked off by Bill Colmers (Edmonton), who provided a succinct review of the neurohormonal regulation of energy homeostasis and its importance for survival. While there was no evolutionary pressure to not exceed the minimum needs, biology favoured the ability to opportunistically store excess energy and defend body weight. While the former is the job of the hedonic system (thus, promoting weight gain), the latter is the job of the homeostatic system (thus, promoting weight regain).

Andres Thalheimer (Wuerzburg, Germany) discusses how olfactory sense and taste may change following bariatric surgery. While anecdotally, patients undergoing surgery often report changes in appetite and response to food stimuli, whether or not these changes are accompanied by changes in gustation or olfaction are less clear. In their own studies, they found a slightly lower olfaction threshold in patients following sleeve gastrectomy but not following Roux-en-Y gastric bypass. However, these preliminary data are far from conclusive and there is a need for significantly more work in this area.

Christian Jurowich (Wuerzburg) presented novel findings on changes in intestinal glucose transport in animal models of bariatric surgery in diabetic rodents. His work focussed on the Na+-D-glucose Cotransporter SGLT1, a pivotal mechanism for intestinal glucose absorption and glucose-dependent incretin secretion and shows how adaptation of this transporter may affect glucose transport and incretin secretion post surgery.

Michael Lyon (Vancouver) reviewed the many biological functions of dietary fibre on a wide range of health conditions ranging from ischemic heart disease, stroke atherosclerosis, type 2 diabetes, overweight and obesity, insulin resistance, hypertension, dyslipidemia, as well as gastrointestinal disorders such as diverticulosis, irritable bowel disease, colon cancer, and cholelithiasis. The physiological effects of fiber relate to the physical properties of volume, viscosity and water holding capacity that the fiber imparts to food leading to important influences over the energy density of food. Beyond these physical properties, fiber directly impacts a complex array of microbiological, biochemical and neurohormonal effects directly through modification of the kinetics of digestion and through its metabolism into constituents such as short chain fatty acids which are both energy substrates and important enteroendocrine ligands. Of particular interest to clinicians is the important role dietary fiber plays in glucoregulation, appetite, and satiety.

Other talks on day 2 of ISORAM included a session on the psychosocial aspects of bariatric care, including a talk by Birgit Wagner (Leipzig) on the complex issue of suicidality, depression, and anxiety disorder particularly in adolescents with severe obesity, a discussion of the many psychological and social issues relevant to the management of childhood obesity and family interventions, and a talk by Almut Rudolph (Lepizig) on the need for pre and post-surgical psychosocial support and interventions in patients undergoing bariatric surgery.

Another talk deserving special mention was a presentation by Tina Ullrich (Edmonton/Leipzig) on some of the mechanisms involved in the development of endothelial dysfunction in childhood obesity – a topic of interest given the early impact that obesity can have on cardiovascular function, thus setting the stage for future complications.

AMS
Lake Louise, Alberta

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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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