Friday, June 27, 2014

Canadians Embark on Landmark Study on Managing Childhood Obesity

sharma-obesity-kids-scale2In line with  global trends, there is considerable concern in Canada on the rising prevalence of childhood obesity.

While much work continues to focus on preventing childhood obesity, far less is known about managing it.

Now, a virtual who-is-who of pediatric obesity researchers and clinicians from across Canada have embarked on a creating the CANadian Pediatric Weight Management Registry (CANPWR), the protocol of which appears in BMC Pediatrics.

CANPWR has three primary aims:

1. To document changes in anthropometric, lifestyle, behavioural, and obesity-related co-morbidities in children enrolled in Canadian pediatric weight management programs over a three-year period;

2. To characterize the individual-, family-, and program-level determinants of change in anthropometric and obesity-related co-morbidities;

3. To examine the individual-, family-, and program-level determinants of program attrition.

This prospective cohort, multi-centre study will include 1,600 children (2 – 17 years old with a BMI >=85th percentile) enrolled in eight Canadian pediatric weight management centres.

Data collection will occur at presentation and 6-, 12-, 24-, and 36-months follow-up.

Although the primary study outcomes are BMI z-score and change in BMI z-score over time a number of secondary outcomes including other anthropometric (e.g., height, waist circumference,), cardiometabolic (e.g., blood pressure, lipid profile, glycemia), lifestyle (e.g., dietary intake, physical activity, sedentary activity), and psychosocial (e.g., health-related quality of life) variables will also be assessed.

The researchers will also examine potential determinants of change and program attrition including individual-, family-, and program-level variables.

I am certain that the findings will be of considerable interest not just in terms of helping us better understand exactly how childhood obesity is being effectively managed in Canada (or not) but also provide important insights for planning future obesity management services for kids with overweight and obesity.

@DrSharma
Vancouver, BC

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Tuesday, June 24, 2014

Time To Go Nuts About Nuts?

sharma-obesity-nutsNuts are reportedly chock full of all kinds of nutrients and are probably among the healthiest of snacks. However, they are also among the most calorie-dense foods – a small handful of nuts (~30 g) can easily add up to 150-200 cals.

So, do high consumers of nuts run the risk of weight gain?

This issue is discussed in depth by Sze Yen Tan and colleagues in a paper published in the American Journal of Clinical Nutrition, in which they review the effects of nuts on appetite, food intake, metabolism, and body weight.

While eating nuts may not exactly lead to weight loss, most studies find that consumption of “extra” calories as nuts leads to substantially less weight gain than may be expected based on their caloric content.

Their review reflect a number of ways in which nuts may have this effect:

Effect on hunger and appetite:

“…nut ingestion suppresses hunger and desire to eat and promotes fullness. These sensations may aid dietary compensation that offsets much of the energy contributed by nuts. However, strong compensation can also occur independently of reported appetitive effects. This may reflect imprecision in appetite measurement or a truly independent uncharacterized mechanism.”

Mastication (chewing):

“Nuts require considerable oral processing effort and this may, in part, account for the often-noted less-than-predicted effect of their consumption on body weight. The mechanical act of chewing reportedly generates satiation signals through cognitive, neural, endocrine, and physical (eg, gastric emptying) mechanisms; augments cephalic phase responses linked to appetite; influences digestion efficiency; modestly increases energy expenditure; and elicits dietary compensation.”

Nutrient absorption:

“A number of studies have evaluated the efficiency of energy absorption from ground and tree nuts through feeding trials. All showed substantive increases in fecal fat loss with nut consumption, although the values ranged widely from ∼5% to >20%”

Energy expenditure:

“Collectively, there is some evidence that nut consumption increases thermogenesis, but the data are not robust and there is no clear mechanism. One possibility is that the lipid from nuts is absorbed over a prolonged period of time, leading to a small but sustained source of substrate that fuels thermogenesis and could appear as an increase in REE.”

Fat metabolism:

“It has been proposed that nut consumption elevates fat oxidation and preferentially reduces body fat mass, especially in the viscera. These actions are attributed to their high unsaturated fat content….Human studies incorporating different nuts into the diet at realistic doses are needed to determine the effect of nut consumption on body composition.”

With regard to impact on body weight, the authors reach the following conclusions:

Adding nuts to habitual diets:

“Although there are reports of small, but significant increases in body weight with nut consumption, the preponderance of evidence indicates that under controlled or free-living situations, nut consumption does not promote weight gain.”

Eating nuts in calorie-restricted diets:

“The inclusion of nuts in energy-restriction regimens does not impede weight loss. In several trials in which nuts did not augment weight loss, there was a reduction in cardiovascular disease risk indexes in the nut-consuming groups, suggesting that such benefits derive from properties of the nuts rather than just weight change.”

Eating nuts in weight maintenance:

“Several studies assessing the role of nut consumption in weight-maintenance programs have noted a decrease in body weight from baseline. Whether this is due to a greater thermic effect of food or REE effect of the nuts compared with the foods they displaced in the diet has not been established. Nevertheless, current data indicate that the inclusion of nuts in a weight-maintenance program will not lead to weight gain and may aid weight loss.”

Thus, in summary, the authors conclude that,

“…evidence indicates that they pose little challenge to and may even aid weight management. This is attributable to the strong dietary compensation effects they elicit, inefficiency in the absorption of the energy they provide, and possibly an elevation of energy expenditure and fat oxidation.”

As a general caveat to all of these data, it needs to be noted that results varied widely depending on the types of nuts and how exactly these nuts were consumed (e.g. as snacks or added to meals – the former often being more favourable than the latter).

Also, many of the studies had relatively small number of participants and were of rather short duration.

Nevertheless, it does appear that going nuts about nuts may not be quite as detrimental to your weight as their energy content would suggest.

@DrSharma
Toronto, ON

ResearchBlogging.orgTan SY, Dhillon J, & Mattes RD (2014). A review of the effects of nuts on appetite, food intake, metabolism, and body weight. The American journal of clinical nutrition, 100 (Supplement 1) PMID: 24920033

 

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Friday, June 20, 2014

Your Body Thinks Obesity Is A Disease

sharma-obesity-adipose-tissue-macrophageYesterday, the 4th National Obesity Student Summit (#COSM2014) featured a debate on the issue of whether or not obesity should be considered a disease.

Personally, I am not a friend of such “debates”, as the proponents are forced to take rather one-sided positions that may not reflect their own more balanced and nuanced opinions.

Nevertheless, the four participants in this “structured” debate, Drs. Sharon Kirkpatrick and Samantha Meyer on the “con” team and Drs. John Mielke and Russell Tupling on the “pro” team (all from the University of Waterloo) valiantly defended their assigned positions.

While the arguments on the “con” side suggested that “medicalising” obesity would detract attention from a greater focus prevention while cementing the status quo and feeding into the arms of the medical-industrial complex, the “pro” side argued for better access to treatments (which should not hinder efforts at prevention).

But a most interesting view on this was presented by Tupling, who suggested that we only have to look as far as the body’s own response to excess body fat (specifically visceral fat) to determine whether or not obesity is a disease.

As he pointed out, the body’s own immunological pro-inflammatory response to excess body fat, a generic biological response that the body uses to deal with other “diseases” (whether acute or chronic) should establish that the body clearly views this condition as a disease.

Of course, as readers are well aware, this may not always be the case – in fact, the state of “healthy obesity” is characterized by this lack of immunological response both locally within the fat tissue as well as systemically.

Obviously, it will be of interest to figure out why some bodies respond to obesity as a disease and others don’t – but from this perspective, the vast majority of people with excess weight are in a “diseased” state – at least if you asked their bodies.

While this is a very biological argument for the case – it is indeed a very insightful one: it is not the existence of excess body fat that defines the “disease” rather, how the body responds to this “excess” is what makes you sick.

As readers, are well aware, there are several other arguments (including ethical and utilitarian considerations) that favour the growing consensus on viewing obesity as a disease.

Of course,  calling obesity a disease should not detract us from prevention efforts, but, as I often point out, just because be treat diabetes or cancer as diseases, does not mean that we do not make efforts to prevent them.

If calling obesity a disease increases resources towards better dealing with this problem and helps take away some of the shame and blame – so be it.

@DrSharma
Waterloo, Ontario

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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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Thursday, June 12, 2014

Lack of Oxygen Can Trigger Adipose Tissue Inflammation

sharma-obesity-adipocytes3Lack of oxygen is a well known stressor for any living cell – this is of course also true for fat cells (adipocytes).

But lack of oxygen does not just occur when there is a problem with breathing or blood flow. Lack of oxygen (hypoxia) can also occur a the cellular level, when the cellular oxygen demand exceeds supply.

According to what may well be considered  a “landmark” paper by Lee and colleagues, published in CELL, it appears that increased adipocyte oxygen consumption may be the key trigger of molecular changes that cause local inflammation and systemic insulin resistance commonly associated with obesity.

The paper reports on a series of animal studies with diet-induced obesity (through a high-fat diet), demonstrating that with increasing weight gain, adipocyte respiration in the mitochondria becomes “uncoupled” leading to a significant increase in oxygen consumption with relative hypoxia.

This uncoupling appears to be mediated through activation of adenine nucleotide translocase 2 (ANT2), an inner mitochondrial membrane protein, by saturated fatty acids.

The resulting hypoxia, in turn, activates the transcription factor HIF-1α, setting off a pro-inflammatory response which in turn leads to insulin resistance with an increased risk of diabetes.

The researcher also show that blocking either ANT2 or HIF-1α can prevent these events, thereby suggesting new pharmacological targets for alleviating the pro-inflammatory and metabolic consequences of obesity.

Obviously, there is always room for caution in extrapolating animal findings to humans, but this paper is likely to spawn a flurry of similar work in human fat cells.

As cellular hypoxia is more likely to occur the larger the fat cell, these studies also tie in the previous observations of a positive association between adipocyte cell size and metabolic abnormalities.

Certainly a topic we can expect to hear more of in the not too distant future.

@DrSharma
Edmonton, AB

ResearchBlogging.orgLee YS, Kim JW, Osborne O, Oh da Y, Sasik R, Schenk S, Chen A, Chung H, Murphy A, Watkins SM, Quehenberger O, Johnson RS, & Olefsky JM (2014). Increased Adipocyte O2 Consumption Triggers HIF-1α, Causing Inflammation and Insulin Resistance in Obesity. Cell, 157 (6), 1339-52 PMID: 24906151

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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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