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Health at a Glance 2009: OECD Indicators
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branch 2. Non-medical Determinants of Health
  branch 2.4. Overweight and obesity among children

Children who are overweight or obese are at greater risk of poor health in adolescence and in adulthood. Being overweight in childhood increases the risk of developing cardiovascular disease or diabetes, as well as related social and mental health problems. Excess weight problems in childhood are associated with an increased risk of being an obese adult, where certain forms of cancer, osteoarthritis, a reduced quality of life and premature death can be added to the list of health concerns (Currie et al., 2008; WHO Europe, 2007).

Evidence suggests that even if excess childhood weight is lost, adults who were obese children retain an increased risk of cardiovascular problems. And although dieting can combat obesity, children who diet are at a greater risk of putting on weight following periods of dieting. Eating disorders, symptoms of stress and postponed physical development can also be products of dieting.

Across most OECD countries, one in seven children are overweight or obese (Figure 2.4.1). Aggregate -figures for 2005-06 show that nearly one in three children in the United States, and one in five in Canada, are overweight or obese - the highest rates among surveyed countries in the OECD. Southern European countries such as Portugal, Greece, Italy and Spain also have higher rates of children with excess weight problems. Fewer than one in ten children in the -Netherlands, Switzerland, the Slovak Republic and Denmark are overweight or obese.

There is no clear association between weight problems and weight reduction behaviours at the national level. In most countries, the number of children trying to lose weight is greater than the number with excess weight problems. Generally, countries where few children report excess weight problems also report weight reduction behaviours close to the OECD average. The six countries with the highest rates of overweight and obese children have similar levels of weight reduction behaviour, each around the OECD average of 14%, even though the proportion of children with excess weight problems varies widely.

There are important differences among children with excess weight problems, according to their age. In some countries older children have more excess weight than younger children, for others countries the opposite is true (Figure 2.4.2). Countries in the top right hand corner of the figure report cohort changes above the OECD average for both boys and girls. A number of countries, including the Netherlands, -Norway, Sweden, Iceland and Switzerland report increases in overweight and obesity rates for both boys and girls as children get older. Eight countries have below average differences for both boys and girls. The Czech Republic stands out as the only -country where rates of excess weight for both boys and girls are lower for the 15-year-old cohorts -compared to the 11-year-old cohorts

Rates of overweight and obese boys and girls are increasing across the OECD (Figure 2.4.3). Between 2001-02 and 2005-06, every surveyed country reported an increase in overweight or obesity for boys aged 15. The largest increases during the four year period were found in the United States, Portugal and Austria. A similar pattern of increases is seen for girls, with rates in the United States, Portugal and Germany almost doubling. Only Ireland and the United Kingdom report reductions in the proportion of overweight or obese girls at age 15 between 2001-02 and 2005-06. However, because non-response rates to questions of self-reported height and weight were high in both these countries, cautious interpretation is required.

Definition and deviations

Estimates of overweight and obesity are based on Body Mass Index (BMI) calculations using child self-reported height and weight. Overweight and obese children are those whose BMI is above a set of age- and sex-specific cut-off points (Cole et al., 2000). Data on weight reduction record children who report being on a diet or doing something else to lose weight.

Self-reported height and weight is subject to under-reporting and error, and requires cautious interpretation. In 2005-06, Canada, England and Norway have missing data for over 30% of res-pondents for 11-year-olds. The same is true for -England, Ireland and Belgium for 13-years-olds, and in England and Ireland for 15-year-olds. In 2001-02, BMI data are missing for over 30% of respondents in Ireland.

Indicators are taken from the Health Behaviour in School-aged Children Surveys in 2001-02 and 2005-06. Aggregate country estimates are crude rates of overweight and obese 11-, 13- and 15-year-olds in each country. Some countries report regional data only. Data are drawn from school-based samples. The survey was not -carried out in Australia, Japan, Korea, Mexico and New Zealand.

 
Indicator in PDF Acrobat PDF page

Figures
2.4.1. Children aged 11-15 years who are overweight or obese, and children who are involved in weight‐reduction behaviour, 2005-06 Figure in Excel
Children aged 11-15 years who are overweight or obese, and children who are involved in weight‐reduction behaviour, 2005-06
2.4.2. Percentage difference in obesity rates between 11 and 15 years by sex, 2005-06 Figure in Excel
Percentage difference in obesity rates between 11 and 15 years by sex, 2005-06
2.4.3. Change in obesity rates between 2001-02 and 2005-06, for 15-year-old boys and girls Figure in Excel
Change in obesity rates between 2001-02 and 2005-06, for 15-year-old boys and girls