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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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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Monday, June 2, 2014

There Has Not Been A Single Success Story in National Obesity Prevention in The Past 33 Years

sharma-obesity_global_obesity_mapJust back from the 21st European Congress on Obesity, I missed out on 100s of media interviews I could have done last week as the media were abuzz with the latest obesity statistics from around the world.

In what will clearly be considered a “landmark” paper by ~150 authors published in The Lancet, we now have the latest summary of global, regional and national data on obesity.

Based on the analyses of almost 1800 surveys, reports, and published studies, the worldwide prevalence of adults with a body-mass index (BMI) of 25 kg/m2 or greater increased between 1980 and 2013 from 29 6o 37% in men and from 30 to 38% in women.

In 2013, 23% of children and adolescents in developed countries were overweight or obese while the same is true for about ~12% of kids in developing countries.

Together, this leave about 2.1 billion of the world populations as currently overweight or obese with numbers growing in virtually every region of the world (albeit with a bit of a slow down in developed countries).

Thus, the authors conclude that,

Not only is obesity increasing, but no national success stories have been reported in the past 33 years.

Obviously, there are many reasons why we lack success stories.

No doubt, one could point to governments that have not tried hard enough, or the food and leisure industry that sustains its overwhelming influence on consumer “choices”, or the continuing “westernization” of global lifestyles.

No doubt, many policies have been tried (e.g. fat taxes, menu labelling, school food programs, fitness taxes, BMI report cards as well as more drastic “shame and blame” tactics) but conclusive evidence that any such measures are working to reverse the tide remains elusive.

It may well be that the flattening of obesity (but not severe obesity) rates in developed countries may have more to do with the “natural” history of this epidemic, than with any public health measures.

On the other hand, perhaps the reason so little progress has been made in preventing obesity is that we are not going after the right targets, namely to change the actual life experiences of overworked, sleep deprived, stress-out families living in a culture of “grabbing a bite” and “working lunches” at one end and the millions living with poor education and food insecurity at the other. No amount of fiddling with menu labelling is about to change that.

What is sad in all of this is the simple fact that virtually no government has yet developed a comprehensive plan on how to improve access to obesity treatments for its populations. Rather, overweight and obese people the world over continue to be denied medical care for this disease on the simple basis that it is their own “fault”.

So while the world awaits the wonder of “prevention” to hopefully one day work its magic, millions of people around the world continue struggling on their own with no help in sight.

Let me guess what will happen as a result of these new numbers – not much!

@DrSharma
Edmonton, Alberta

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Thursday, May 22, 2014

Canada’s Bubble-Wrapped Kids Need More Free Play

sharma-obesity-active-healthy-kidsNo doubt Canadian parents think physical activity and sports is of utmost importance for their kids’ health – this is why, they have apparently sold them off to the multi-billion dollar sport and fitness industrial complex that has pretty much commercialized all aspects of physical activity.

This is why good ol’ get out doors and play (without your parents hand holding you, peering over your shoulder or tracking your whereabouts on GPS) is pretty much dead.

At least this is the gist of the latest Physical Activity Report Card presented by Active Healthy Kids Canada.

Here are some of the main findings:

Canadian parents look to structured activities and schools to get their kids moving:

- 82% of parents agree that the education system should place more importance on providing quality PE.

-  79% of parents contribute financially to their kids’ physical activities (through equipment, fees, etc.), but only 37% of parents often play actively with their children.

Organized sports and plenty of places and spaces for activity may never make up for lost (active) time:

- One study shows only 24% of kids got a full 60 minutes of moderate/ vigorous activity in one session of soccer, and only 2% got this at softball practice.

- Kids on hockey teams spend close to half of the time during practices in moderate/vigorous activity, but in an actual game they are sedentary nearly a third of the time.

So if you think you are doing your kids a favour by putting them in organiszed sporting activities, that break both your time and money budget, then think again.

Your kids may be way better off if you just kicked them outdoors (not to be seen again till the lights come on).

@DrSharma
Barcelona, ES

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Wednesday, May 21, 2014

Does Calling You Fat Make You Fat?

sharma-obesity-discriminationOne of the most troubling aspects of weight-bias and discrimination is that it has strong negative emotional and physical consequences for the individuals, who perceive these negative attitudes.

Now a study suggests that simply being labeled “fat” in childhood may be a strong predictor of obesity ten year later.

Thus, according to a longitudinal study by Jeffrey Hunger and Janet Tomiyama, published in JAMA Pediatrics, girls who reported being called “fat” at age 10 were about 60% more likely to have a BMI in the obese range at age 19.

Kids in this study were considered as “labeled”, if they responded “yes” to the question, whether they had ever been called fat by their father, mother, brothers, sister, best girl friend, boy you like best, any other girl, any other boy, or teacher.

Interestingly enough, this finding is not explained by the possibility that the labelled girls were indeed heavier – there was in fact no difference in BMI at age 10 between the kids who responded “yes” and those, who did not.

Indeed, the findings remained robust even after correction for various demographic confounders.

These findings are concerning, as they suggest that simply being called “fat” as a kid, may put you on a track to weight gain irrespective of whether or not you actually carry excess weight to start with.

I am sure many of my readers will relate to these findings and can tell their own stories of how being “labelled” fat may have influenced their weight journeys.

@DrSharma
Edmonton, AB

ResearchBlogging.orgHunger JM, & Tomiyama AJ (2014). Weight Labeling and Obesity: A Longitudinal Study of Girls Aged 10 to 19 Years. JAMA pediatrics PMID: 24781349

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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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