Establishing a standard definition for child overweight and obesity worldwide
Dear Sir,
Childhood obesity is a new challenge in both the developed and developing world. However, the data on prevalence in various populations in children and adolescence were very much lacking because there was no simple and good cut off for the measurement of obesity in childhood, unlike in adult.
Dr. TJ Cole and colleagues (BMJ, 6 May, 2000) proposed a standard definition for child overweight and obesity, basing on six large international growth surveys, Hong Kong being one of these(1).
As one of the workers of the Hong Kong growth survey, I would like to congratulate the authors making a very good point that any such cut off should coincide with that of adult at age 18. However, there are three points that I would like to raise for further discussion.
First, children are unique in their complicated issue of growth so that description of their weight and height is usually age specific. Body fat accumulation has four physiological phases(2) and obesity is usually an exaggeration of the prepubertal phase. Paediatricians who look after obese children are familiar with a typical information given by parents that 'their child put on weight rapidly after the age of 5 years.' That is why obesity is mainly a problem of childhood and adolescence but rarely of infants and toddlers. It is hence absurd to believe that throughout childhood and adolescence the prevalence of obesity is the same.Therefore, using a uniform centile line across the whole age range of childhood to define obesity is not scientific and can be very misleading. e.g. any infant, toddler or preschooler who has BMI above the 90th centiles might have been advised to have weight control when they were in fact normal.
The Hong Kong growth survey was performed in 1993, basing on 25,000 individuals. 120% median weight for height was used as cut off for obesity(3). Children who were defined obese do look obese by observation. If 120% median BMI was used as cut off for obesity, the prevalence was also quite close, particularly before puberty (Fig.1). The knowledge of the varied prevalence between 0-18 years is also important in designing strategy for the community health services. One obvious deduction is that it is important to help all toddlers and preschoolers to establish healthy diet and life style even before many of them become obese. Whereas for school children, it is important to design exercise programme and healthy meals at school in addition to educating the parents about healthy life style.
Second, the argument for using an international reference for growth assessment in childhood is still ongoing. Studies have shown that Asians develop morbidity related to obesity, such as diabetes mellitus, hypertension and hypercholesterolemia, at a lower BMI compared to the Caucasians (4). Recently WHO recommended a cut off BMI index for Asians: >23-24.9 as overweight and > 25 as obese. For the Caucasians these would be : > 25-29.9 as overweight and > 30 as obese. If Asians were to use the international reference and cut off, then they would easily underestimate the severity of the problem of obesity. If national or ethnically appropriate reference for defining obesity were used we can still compare the prevalence of obesity between populations, be it adults or children.
Last, in the childhood population, the differentiation between overweight and obesity may not have much implication in the management, unlike the adults. Therefore, if 120% median BMI was used for Hong Kong, then at 18 years it would approximate that of 25.
Unless there is a better reason to change the cut off reference, I think Hong Kong can still stick to the use of 120% median BMI or 120% median weight for height. The latter is much more convenient in the clinic setting and the local Student Health Services has been using it to monitor the progression of the problem of childhood obesity since it's establishment in 1997.
Yours sincerely,
Dr. Sophie Leung
Centre for Nutritional Studies,
The Chinese University of Hong Kong
Corresponding address:
Dr. Sophie Leung,Sophie Leung,
Shop G32, MetroCity Phase III,
8, Mau Yip Road,
Tseung Kwan O, Hong Kong
1. Leung SSF, Cole TJ, Tse LY, Lau JYF. Body mass index reference curves for Chinese children. Ann of Hum Bio 1998;25(2):169-74.
2. Leung SSF, Chan SM, Lee WTK, Davies DP. Growth and nutrition of Hong Kong children aged 0-7 years. J. Paed Child Heath 2000;36:56-65.
3. Leung SSF, Lau JTF, Tse LY, Oppenheimer SJ. Weight for age and weight for height reference for Hong Kong children birth -18 years. Aust J. Paediatrics 1996;32:103-9.
4. Ko GTC, Chan JCN, Cockram CS, Woo J. Prediction of hypertension, diabetes, dyslipidaemia or albuminuria using simple anthropometric indexes in Hong Kong Chinese. Int J Obes. 1999;23:1136-42.
5. The Asia Pacific Perspective: redefining obesity and its treatment. Feb 2000. Health Communications Australia Pty Limited.
Competing interests:
No competing interests
20 August 2001
Sophie S F Leung
Centre for Nutritional Studies, the Chinese University of Hong Kong
Rapid Response:
Establishing a standard definition for child overweight and obesity worldwide
Dear Sir,
Childhood obesity is a new challenge in both the developed and developing world. However, the data on prevalence in various populations in children and adolescence were very much lacking because there was no simple and good cut off for the measurement of obesity in childhood, unlike in adult.
Dr. TJ Cole and colleagues (BMJ, 6 May, 2000) proposed a standard definition for child overweight and obesity, basing on six large international growth surveys, Hong Kong being one of these(1).
As one of the workers of the Hong Kong growth survey, I would like to congratulate the authors making a very good point that any such cut off should coincide with that of adult at age 18. However, there are three points that I would like to raise for further discussion.
First, children are unique in their complicated issue of growth so that description of their weight and height is usually age specific. Body fat accumulation has four physiological phases(2) and obesity is usually an exaggeration of the prepubertal phase. Paediatricians who look after obese children are familiar with a typical information given by parents that 'their child put on weight rapidly after the age of 5 years.' That is why obesity is mainly a problem of childhood and adolescence but rarely of infants and toddlers. It is hence absurd to believe that throughout childhood and adolescence the prevalence of obesity is the same.Therefore, using a uniform centile line across the whole age range of childhood to define obesity is not scientific and can be very misleading. e.g. any infant, toddler or preschooler who has BMI above the 90th centiles might have been advised to have weight control when they were in fact normal.
The Hong Kong growth survey was performed in 1993, basing on 25,000 individuals. 120% median weight for height was used as cut off for obesity(3). Children who were defined obese do look obese by observation. If 120% median BMI was used as cut off for obesity, the prevalence was also quite close, particularly before puberty (Fig.1). The knowledge of the varied prevalence between 0-18 years is also important in designing strategy for the community health services. One obvious deduction is that it is important to help all toddlers and preschoolers to establish healthy diet and life style even before many of them become obese. Whereas for school children, it is important to design exercise programme and healthy meals at school in addition to educating the parents about healthy life style.
Second, the argument for using an international reference for growth assessment in childhood is still ongoing. Studies have shown that Asians develop morbidity related to obesity, such as diabetes mellitus, hypertension and hypercholesterolemia, at a lower BMI compared to the Caucasians (4). Recently WHO recommended a cut off BMI index for Asians: >23-24.9 as overweight and > 25 as obese. For the Caucasians these would be : > 25-29.9 as overweight and > 30 as obese. If Asians were to use the international reference and cut off, then they would easily underestimate the severity of the problem of obesity. If national or ethnically appropriate reference for defining obesity were used we can still compare the prevalence of obesity between populations, be it adults or children.
Last, in the childhood population, the differentiation between overweight and obesity may not have much implication in the management, unlike the adults. Therefore, if 120% median BMI was used for Hong Kong, then at 18 years it would approximate that of 25.
Unless there is a better reason to change the cut off reference, I think Hong Kong can still stick to the use of 120% median BMI or 120% median weight for height. The latter is much more convenient in the clinic setting and the local Student Health Services has been using it to monitor the progression of the problem of childhood obesity since it's establishment in 1997.
Yours sincerely,
Dr. Sophie Leung
Centre for Nutritional Studies,
The Chinese University of Hong Kong
Corresponding address:
Dr. Sophie Leung,Sophie Leung,
Shop G32, MetroCity Phase III,
8, Mau Yip Road,
Tseung Kwan O, Hong Kong
Email: ssfleung@netvigator.com
References:
1. Leung SSF, Cole TJ, Tse LY, Lau JYF. Body mass index reference curves for Chinese children. Ann of Hum Bio 1998;25(2):169-74.
2. Leung SSF, Chan SM, Lee WTK, Davies DP. Growth and nutrition of Hong Kong children aged 0-7 years. J. Paed Child Heath 2000;36:56-65.
3. Leung SSF, Lau JTF, Tse LY, Oppenheimer SJ. Weight for age and weight for height reference for Hong Kong children birth -18 years. Aust J. Paediatrics 1996;32:103-9.
4. Ko GTC, Chan JCN, Cockram CS, Woo J. Prediction of hypertension, diabetes, dyslipidaemia or albuminuria using simple anthropometric indexes in Hong Kong Chinese. Int J Obes. 1999;23:1136-42.
5. The Asia Pacific Perspective: redefining obesity and its treatment. Feb 2000. Health Communications Australia Pty Limited.
Competing interests: No competing interests