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Fast Facts on� Obesity in Durham Region�s Youth by rrboy

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									                                                 Fast Facts on…
                                Obesity in Durham Region’s Youth

Defining Overweight and Obesity in Children and Youth
  Normal growth, puberty and body composition changes make defining overweight and obesity
  in children and youth more complicated than adults.
  Skin fold measurements and weight-for-height charts have been used to classify overweight
  and obese children and youth. However, body mass index (BMI) is the most accepted and
  currently the most widely used measure.


What is Body Mass Index?
  Body mass index (BMI) classifies weight-to-height ratios into ranges associated with health
  risk categories for adults. It is calculated by dividing weight (in kilograms) by height squared
  (in metres), i.e. BMI = kg/m2.
  BMI is not intended for children and youth unless it is adjusted for age (see below). It is
  also not intended to be used for pregnant and lactating women.
  BMI categories for adults are:
      BMI of 18.5 - 24.9 - an acceptable or healthy weight,
      BMI of 25.0 – 29.9 - overweight category,
      BMI of 30.0 or more - obese category,
      BMI of less than 18.5 – underweight category.
  Special consideration may be needed when using the categories for specific groups such as
  highly muscular adults and young adults who have not reached full growth.
  Some health problems associated with overweight and obesity include: Type 2 diabetes, high
  cholesterol, high blood pressure, heart disease, gallbladder disease, arthritis, obstructive
  sleep apnea, and certain cancers.
  Some health problems associated with underweight, which may indicate an eating disorder or
  underlying illness, include under-nutrition, osteoporosis, infertility, and impaired immune
  system problems.
  Since people tend to underestimate their weight and overestimate their height, the values
  of BMI based on self-reported weight and height are probably low. Studies estimate that
  obesity would be approximately one and a half times more prevalent if calculations were
  based on observed data, that is, measured height and weight.


How is BMI Calculated Differently in Children and Youth?
  Height and body composition in children and youth are continually changing. BMI increases
  sharply in infancy, falls during the preschool years to a minimum around 4-6 years, then rises
  again into adulthood.
  BMI-for-age is recommended for children aged two years and older as this measure
  accounts for age and sex differences in weight, height and body composition that occur
  during childhood and youth.
  The following are the BMI-for-age classifications (based on growth and BMI index charts
  developed by the Centers for Disease Control and Prevention in the United States (CDC));
      normal weight (5th to below the 85th percentile),
      overweight (85th to below the 95th percentile),
      obese (95th percentile or greater),
      underweight (below the 5th percentile).
  There is considerable variability in the studies on overweight and obesity in children and
  youth. In this report, CDC’s BMI-for-age classification is used to describe the prevalence of
  overweight and obesity in youth aged 12-19 years. Other studies using different
  methodologies or BMI classification of overweight and obesity are included, not for
  comparison purposes, but to provide further evidence to support that overweight and
  obesity is a serious public health concern and the prevalence of overweight and obesity has
  increased over the past two decades.
  Terminology for the BMI-for-age classification can also vary;
      overweight (85th to below the 95th percentile) - ‘at risk for overweight’,
      obesity (95th or greater percentile) - ‘overweight’.
  In this report, the overweight and obesity terminology is used throughout.


Prevalence of Overweight and Obesity in Youth Aged 12-19 Years
  Internationally: Results from the 1999-2002 National Health and Nutrition Examination
  Survey (NHANES) in the United States estimated that 30% of youth aged 12-19 years were
  overweight. For the same age group, 16% were obese, a 45% increase from an estimated 11%
  obesity prevalence found in the 1988-1994 NHANES. These results are based on measured
  height and weight.
  Nationally: According to the Canadian Community Health Survey (CCHS) 2000/01, 17% of
  Canadian boys and 10% of Canadian girls aged 12-19 years were overweight. For the same age
  group, the proportions who were obese were 6% and 3% for boys and girls, respectively. All
  CCHS results are based on self-reported height and weight.
  Provincially: In Ontario, 19% (95%CI=2%)** of youth aged 12-19 years were overweight or
  obese (CCHS 2000/01). Boys were more likely to be overweight or obese; 24% (95%CI=2%)
  compared to 15% (95%CI=2%) for girls.
  Locally: Similar to the provincial estimate, 15% (95%CI=7%) of Durham Region youth aged
  12-19 years were overweight or obese. Sex-specific estimates were not possible due to the
  small sample.


Changes over time …
  Provincial and local surveillance data are only available for the past decade. Between 1990
  and 2000/01, the prevalence of overweight or obesity in Durham Region and Ontario youth
  aged 12-19 years has remained unchanged. This is consistent with the 2004 report from the



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  Canadian Institute of Health Information, Improving the Health of Canadians, suggesting
  that the rates of overweight and obesity in youth may have stabilized in the last few years.


                % Youth Aged 12-19 Years Who Are Overweight or Obese,
                             Durham Region and Ontario
       80
                                                                   Durham       Ontario
       60


    % 40
                   *                                                       *
                  16.3 18.9                   20.0 19.9                          19.4
       20                                                                15.3

        0
                    OHS 1990                  OHS 1996/07                 CCHS 2000/01


  Source: Ontario Health Survey 1990, 1996/97, Canadian Community Health Survey 2000/01
  *interpret with caution due to high variability, CV*** between 16.6-33.3.


Other Evidence      (different age groups, BMI classifications or collection methods)
  A study by Popkin et al in 1996 demonstrated that the problem of overweight and obese
  children is worldwide. (The BMI classification used weight-for-height charts and measured
  height and weight.)

                    Prevalence of overweight* children aged 6-8 year olds

                                 USA China Russia South Africa Brazil
                               1988-91 1993 1994-5   1994      1989

                       Girls    24.2   12.2    17.8         20.3        10.5

                       Boys     21.3   14.1    25.6         25.0        12.8

                    (*defined as BMI higher than the 85th percentile)


  According to the World Health Organization’s cross-national study, Health Behaviours in
  School-Aged Children (HBSC), in the report by William Boyce, Young People in Canada: Their
  Health and Well-Being, between 15-22% of Canadian boys aged 11-15 years (single year age
  groupings) were overweight and a further 5-7% were classified as obese across the age
  groups. For Canadian girls, in the same single year age groupings, 11-14% were overweight and
  2-4% were obese. In this report, BMI classifications were based on internationally pooled


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data, linked to adult obesity cut off points and herein referred to as ‘International
Standards’ (Cole at al, 2000). (These data used self-reported height and weight)
According to Tremblay et al (2000), between 1981 and 1996, the prevalence of overweight
Canadian boys aged 7-13 years increased from 15% to 35% and among girls from 15% to 29%.
The prevalence of obesity tripled during the same time period, from 5% in both sexes to
17% for boys and 15% for girls. BMI was classified in this report using the 85th and 95th
percentile cut points based on a 1981 Canadian reference population (measured height and
weight (1981) and parent-reported/self-reported height and weight (1996)). A subsequent
study by Tremblay et al (2002) using the International Standards for classifying BMI
reaffirmed these findings and suggested that the prevalence of childhood obesity had
increased five-fold. International comparisons were also possible; the prevalence of
overweight in Canadian childhood exceeded that in Britain and Spain.

          Comparison Of The Prevalence Of Overweight Among Canadian,
      Scottish, English and Spanish Children Aged 7-8 Years and 9-11 Years.

                             1980-1984                      1994-1996
                        7-8 yrs.    9-11 yrs.      7-8 yrs.        9-11 yrs.
        Males
        Canada            7.5          13.7          38.9            30.2
        Scotland          6.4          6.9           8.0             13.4
        England           5.7           5.8          9.0             12.7
        Spain              -           11.0           -              25.6
        Females
        Canada            15.7         11.8          33.0            26.7
        Scotland          11.3         10.6          15.1            19.6
        England           10.6          9.9          12.5            16.7
        Spain              -           15.2           -              21.6

From the National Longitudinal Survey of Children and Youth, 34% of Canadian children aged
2-11 years were overweight including 16% who were classified as obese in 1994/95. By
1998/99, 37% of children in the same age group were overweight, with 18% classified as
obese. (This survey used International Standards and parental report of height and weight.)

According to the 2004 Chief Medical Officer of Health Report, Healthy Weights, Healthy
Lives, 19.3% of Ontario boys and 10.8% of girls aged 12-18 years were overweight and a
further 4.2% and 3.4% of boys and girls, respectively, were classified as obese in 1990. The
proportion of children who were overweight or obese remained relatively stable through the
1990s. In 2000, 19.1% of boys and 11.1% of girls were classified as overweight and a further
5.2% of boys and 3.3% of girls were obese. (This report used International Standards and
self-reported height and weight.)




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Local Initiatives to Measure BMI in Children
   Simcoe County District Health Unit, in collaboration with the Simcoe County District School
   Board and the Simcoe Muskoka Catholic District School Board conducted a cross- sectional
   survey among grade one Simcoe County students. In 2003, 16% were overweight and 10%
   were obese. (This study used CDC’s classification and measured height and weight.)
   The Northern Ontario Perinatal and Child Health Survey Consortium conducted a cross-
   sectional telephone survey targeting Northern Ontario mothers of children aged 0-6 years.
   In 2002, 17% of Northern Ontario children aged 2-6 years old were overweight and 30%
   were classified as obese. (Here, CDC’s classification was used with parental report of height
   and weight.)
   The Porcupine Health Unit conducted a cross-sectional survey of Timmins students aged 6-
   17 years. In 2004, 7% were overweight and 14% were classified as obese. ( The survey used
   CDC’s classification and measured height and weight.)


Summary
   Body mass index (BMI) is the most accepted and currently the most widely used measure of
   healthy weight.
   BMI in children and youth is calculated differently than in adults to account for differences
   in weight, height and body composition that occur during childhood and youth.
   Caution should be used when comparing BMI results for children and youth from different
   studies as there is considerable variation in BMI classification, data collection methods, and
   age groupings. Regardless of the classification or methods used, the findings across studies
   suggest that:
       rates of overweight and obesity tend to be higher in boys,
       overweight and obesity are prevalent in young children and youth,
       rates of overweight and obesity have increased since the 1980s although recent data
       suggest that estimates may have stabilized in the past few years.
   In Durham Region, 15% of youth aged 12-19 years were overweight or obese in 2000/01.
   This is similar to Ontario’s estimate of 19%.
   Since 1990, the prevalence of overweight and obesity in Durham Region youth has remained
   stable.


Key Resources
A collaborative statement from Dietitians of Canada, Canadian Paediatric Society, The College
of Family Physicians of Canada, and Community Health Nurses Association of Canada. The use of
growth charts for assessing and monitoring growth in Canadian infants and children. Canadian
Journal of Dietetic Practice and Research 2004; 65(1): 22-32. Available at
http://www.dietitians.ca/news/downloads/position_growth_charts_children_March2004.pdf

Body Mass Index (BMI) for Children and Adolescents. Available at
http://www.apheo.on.ca/indicators/index.html




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Boyce, WF. Young People In Canada: Their Health And Well-Being. Available at
http://www.phac-aspc.gc.ca/dca-dea/publications/hbsc-2004/pdf/hbsc_report_2004_e.pdf

Canadian Institute for Health Information. 2004. Improving the Health of Canadians. Available at
http://secure.cihi.ca/cihiweb/dispPage.jsp?cw_page=PG_39_Eandcw_topic=39andcw_rel=AR_322_E

Carriere G. Parent and child factors associated with youth obesity. Health Reports – Supplement
2003; 14: 29-39.

Cole TJ, Bellizzi MC, Flegal KM, Dietz WH. Establishing a standard definition for child
overweight and obesity worldwide: international survey. BMJ 2000; 320(May 6): 1-6. Available
at http://bmj.bmjjournals.com/cgi/content/full/320/7244/1240

He M. Childhood Obesity: A Growing Public Health Concern. A Literature Review, September 28,
2002. Public Health Research, Education and Development Program, Middlesex-London Health
Unit.

Nutrition in Northern Ontario. December 2003. A Report from the Northern Ontario Perinatal
and Child Health Survey Consortium. Available at
http://www.tbdhu.com/reports/Nopchs/NOPCHS%20Nutrition%20Report%20FINAL-Dec-03.pdf


Ogden CL, Flegal KM, Carroll MD, Johnson CL. Prevalence and trends in overweight among US
children and adolescents, 1999-2000. JAMA 2002; 288 (October 9):1728-32. 2002.
Popkin BM, Richards MK, Montiero CA. Stunting is associated with overweight in children of four
nations that are undergoing the nutrition transition. Journal of Nutrition 1996; 26(12): 3009-16.

Prevalence of Childhood Obesity in a Northeastern Ontario City. A Cross-Sectional Study. A
presentation by Foyes Haque, Epidemiologist at the Porcupine Health Unit, at the December 3,
2004 General Meeting of the Association of Public Health Epidemiologists in Ontairo (APHEO).

Tremblay MS, Willms, DJ. Secular trends in the body mass index of Canadian children. CMAJ
2000; 163(11): 1429-33. Erratum 2001; 164(7): 970. Available at
http://www.cmaj.ca/cgi/reprint/163/11/1429 and http://www.cmaj.ca/cgi/reprint/164/7/970

Tremblay MS, Katzmarzk PT Willms, DJ. Temporal trends in overweight and obesity in Canada,
1981-1996. International Journal of Obesity 2002; 26: 538-43.

2004 Chief Medical Officer of Health Report. Healthy Weights, Healthy Lives. Ontario
Ministry of Health and Long-Term Care. Available at
http://www.health.gov.on.ca/english/public/pub/ministry_reports/cmoh04_report/healthy_weig
hts_112404.pdf




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Simcoe County Child Health Survey, Preliminary Report, June 18, 2004. Simcoe County District
Health Unit. Available at http://www.simcoehealth.org/pdfs/report.pdf

Statistic Canada. 2002. National Longitudinal Survey of Children and Youth: Childhood obesity,
1994-1999. The Daily, October 19, 2002. Available at
http://www.statcan.ca/Daily/English/021018/d021018.pdf


**95% Confidence Interval (CI) refers to the range of values that has a 95% chance of including the ‘true’ value. A
wide confidence interval reflects a large amount of variability or imprecision. Usually, the larger the sample size, the
narrower the confidence intervals.
***Coefficient of Variation (CV) refers to the precision of the estimate. When a CV is between 16.6% and 33.3%,
the estimate should be interpreted with caution because of high variability.



Last updated: March 7, 2005




             For more information, contact the Epidemiology and Evaluation Unit,
   Durham Region Health Department, tel: (905) 725-8521, web site: www.region.durham.on.ca

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                                                     Addendum
                                                           Fast Facts on…
                                          Obesity in Durham Region’s Youth

Prevalence of Overweight and Obesity in Youth Aged 12-19 Years:
An Update
    Estimates from the newly released Canadian Community Health Survey (CCHS 2003) showed
    that the prevalence of overweight and obesity in Durham Region youth aged 12-19 years was
    14% (95%CI= ±6%**). Similar results were found in Ontario where 19% (95%CI= ±2%) of
    youth were overweight or obese.
    Since 1990, the prevalence of overweight or obesity in Durham Region and Ontario youth
    aged 12-19 years has remained unchanged.
    These findings are consistent with the released, Fast Facts on Obesity in Durham Region’s
    Youth, March 7, 2005.


                      % Youth Aged 12-19 Years Who Are Overweight or Obese,
                                   Durham Region and Ontario

      80
                                                                                      Durham         Ontario
      60

    % 40            *
                   16.3 18.9                 20.0 19.9                  *
                                                                      15.3 19.4                  *
                                                                                                14.0 18.9
      20

        0
                     OHS 1990                OHS 1996/07              CCHS 2000/01                CCHS 2003
            Source: Ontario Health Survey 1990, 1996/97, Canadian Community Health Survey 2000/01, 2003
            *interpret with caution due to high variability, CV*** between 16.6-33.3



**95% Confidence Interval (CI) refers to the range of values that has a 95% chance of including the ‘true’ value. A
wide confidence interval reflects a large amount of variability or imprecision. Usually, the larger the sample size, the
narrower the confidence intervals.
***Coefficient of Variation (CV) refers to the precision of the estimate. When a CV is between 16.6% and 33.3%,
the estimate should be interpreted with caution because of high variability.




Last updated: June 7, 2005

                   For more information, contact the Epidemiology and Evaluation Unit,
   Durham Region Health Department, tel: 905-668-7711, web site: www.region.durham.on.ca

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