10 May Canadian Children Less Overweight Than Decade Ago

MedicalResearch.com Interview with:

Dr. Atul Sharma

Atul Sharma MD, MSc(Statistics), FRCPC
Researcher, Children’s Hospital Research Institute of Manitoba; Assistant Professor, Department of Pediatrics and Child Health, University of Manitoba; Senior Consultant, Biostatistics Group, George and Fay Yee Center for Healthcare Innovation

MedicalResearch.com: What is the background for this study? What are the main findings?

Dr. Sharma: Between 1978 and 2004, a previous comparison of directly measured heights and weights demonstrated an alarming increase in the prevalence of overweight or obesity in Canadian children aged 2-17y, from 23.3% (95% CI = 20.5-26.0) to 34.7% (33.0-36.4) based on the new 2007 WHO criteria.

In Canada, the definitions of overweight and obesity changed with the introduction of the new ‘2010 WHO Growth Charts for Canada’, Previous definitions were based on Body Mass Index (BMI) percentiles from the 2000 Centers for Disease Control and Prevention (CDC) growth chart’s. In addition to revising the percentile thresholds for diagnosing overweight or obesity, the WHO charts were based on a very different reference population. As a result, the proportion of Canadian children being classified as overweight or obese increased with the introduction of the new WHO charts.

Our current study applied current Canadian definitions of overweight and obesity to a contemporary sample of Canadian children age 3-19y to assess recent trends in the rates of overweight and obesity. By pooling data from the Canadian Community Health Survey (CCHS, cycle 2.2) and the Canadian Health Measures Survey (CHMS, cycles 2 and 3), we were able to study a representative sample of more than 14000 Canadian children from the period 2004-2013.  The sample was evenly split between boys and girls and approximately 80% white.

MedicalResearch.com: What should readers take away from your report?

Dr. Sharma: Canadian children are leaner and less overweight now than a decade earlier, as we observed a decline in the prevalence of overweight or obesity from 30.7% (95% confidence interval [CI] 29.7%–31.6%) in 2004-5 to 27.0% (95% CI 25.3%–28.7%) (p < 0.001) in 2012-13. Over the same period, obesity appeared to stabilize with a prevalence about 13%. These trends persisted after adjustment for age, sex and race/ethnicity and were accompanied by reductions in both weight and BMI z scores. Younger children and girls fared better than males and adolescents.  Nevertheless, Canadian children remain heavier that they were before the North American obesity epidemic. Although they declined, the median z scores for BMI, weight and height were positive and higher than those in the WHO reference population. Curiously, Z scores for waist circumference and waist:height ratio were negative, which indicated that the Canadian children had less central adiposity than American children in historic or contemporary NHANES cohorts.

MedicalResearch.com: What recommendations do you have for future research as a result of this study?

Dr. Sharma: Ongoing research is needed to identify socioeconomic factors that may also be associated with current overweight or obesity rates, to improve our understanding of the pathogenesis and better focus intervention programs where they are most needed. While progress is welcome,  it is also important that we not become complacent, as rates of overweight or obesity are still higher than they were in 1978.  

MedicalResearch.com: Is there anything else you would like to add?

Dr. Sharma: While census data does not allow us to identify the mechanisms responsible for these changes, we can speculate that the introduction of the CDC BMI reference charts in 2000 provided front-line health care workers with an important took with which to engage families in discussions around their children’s weight. Moreover,  intense media scrutiny and public health measures at all levels may also have focused attention on this important health issue and appear to be making a  difference for children.  

MedicalResearch.com: Thank you for your contribution to the MedicalResearch.com community.

Citation:

Celia Rodd, MD, Atul K. Sharma, MD. Recent trends in the prevalence of overweight and obesity among Canadian children. CMAJ, May 2016 DOI: 10.1503/cmaj.150854

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Last Updated on May 10, 2016 by Marie Benz MD FAAD