Obesity is a global problem with increasing prevalence worldwide and this alarming trend is already prevalent during childhood (infants and children up to 19 years of age). The World Health Organization (WHO) states that the number of overweight or obese preschool children aged 0 to 5 years has risen from 32 million in 1990 to 42 million in 2013 globally and is estimated to reach 70 million by 2025.1 Childhood obesity has serious consequences for health and can result in non-communicable diseases at later stages in life. This includes cardiovascular complications and diabetes, as well as premature death.
But how is obesity measured in children? Obesity in infants and children below the age of 5 is evaluated according to the WHO “Child growth standards” (weight-for-length and weight-for-height).2 For school-aged children and adolescents between the age of 5 and 19 years, obesity is assessed through an age-adjusted body mass index (BMI-for-age).3 BMI is a widely used weight-for-height measure that is calculated by dividing a person’s weight in kilograms by the square of the person’s height in meters (kg/m2).4 The BMI-for-age is calculated the same way, however, it is interpreted in relation to the age of the child or adolescent. Thus, a child or adolescent is classified as overweight with BMI-for-age values >1 standard deviation (SD) and as obese with values >2SD from the WHO growth standard median.3
These obesity assessment methods enable researchers to quantify the prevalence and trends of childhood obesity in specific populations of children, for example preschool children living in Asian sub-regions. In this fashion, a study was conducted based on the WHO growth standards that analysed the proportion of overweight and obese preschool children in United Nations (UN)-governed regions including the Asian sub-regions Western, Central, South-Eastern and Eastern Asia (excluding Japan).5
A total of 450 nationally representative cross-sectional surveys from 144 countries were used to evaluate the body weight of preschool children from 0 to 5 years of age.5 Children were categorized as overweight and obese if their weight-for-length value (for children up to 24 months) or weight-for-height value (for children above 24 months) was >2SD and >3SD, respectively, from the WHO growth standard median. They were categorized as “being at risk of overweight” with values >1SD and ≤2SD from the WHO growth standard. Furthermore, the analyses for preschool children showed very similar prevalence results when comparing weight-for-height and BMI-for-age.
In order to estimate prevalence rates and numbers of affected children in 2015 and 2020 a linear mixed-effects model was used that was applied previously for stunted and underweight trend analyses.
According to the study, the estimated prevalence of childhood overweight and obesity in Asia in 2010 was 4.9% (95% confidence interval [CI]: 3.2%, 6.6%) and is expected to reach 6.8% (95% CI: 3.7%, 9.8%) in 2020 (Figure 1).5 The rising trend was particularly evident in Western Asia which had a prevalence of 14.7% (95% CI: 9.8%, 21.6%) in 2010 and is projected to rise to 29.1% (95% CI: 15.3%, 48.3%) in 2020.
In total, it was estimated that there were 17.7 million overweight and obese preschool children in Asia in 2010 (Figure 2).5 From these, Central Asia was predicted to exhibit the largest number of overweight and obese children as more than a third of the children (6.6 million) lives in this region. The estimated total number of preschool children defined as being at risk of overweight in 2010 was 44.2 million with Eastern and Central Asia contributing the highest numbers (19.7 million and 14.5 million, respectively).
- World Health Organization. Facts and Figures on Childhood Obesity. http://www.who.int/end-childhood-obesity/facts/en/. Accessed on 30 December 2015.
- World Health Organization. WHO Child Growth Standards.; 2006.
- World Health Organization. BMI-for-Age (5-19 Years). http://www.who.int/growthref/who2007_bmi_for_age/en/#Accessed on 30 December 2015.
- World Health Organization. BMI Classification. http://apps.who.int/bmi/index.jsp?introPage=intro_3.html. Accessed on 30 December 2015.
- de Onis M, Blössner M, Borghi E. Am J Clin Nutr 2010;92:1257-1264.