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Increasing prevalence of obesity in primary school children: cohort study

Mary C J Rudolf, community paediatrician ^a, Pinki Sahota, senior lecturer in nutrition and dietetics ^b, Julian H Barth, consultant in chemical pathology and metabolic medicine ^c, Jenny Walker, auxologist ^c. 

^a Community Paediatrics, Leeds Community and Mental Health Trust, Leeds LS2 9NP, ^b School of Health Sciences, Leeds Metropolitan University, Leeds LS1 3HE, ^c Regional Paediatric Endocrinology Clinic, Leeds General Infirmary, Leeds LS1 3EX

Correspondence to: M C J Rudolf Mrudolf{at}ulth.northy.nhs.uk

Reports suggest that the prevalence of obesity among children is increasing. Reilly et al reported that, even by the age of 5, the prevalence of obesity was higher than that expected from the national standards¹ and that this persisted into the teenage years.²

	Participants, methods, and results

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From 1996 to 1999 an auxologist (JW) measured children in 10 primary schools in Leeds participating in a health promotion programme.³ Children in years 3 and 4 (age 7-9 years) were measured in July 1996 and again in July 1997 and 1998. These children were marginally more advantaged than average for Leeds, with 1-42% of pupils from ethnic minorities and 7-29% entitled to free school meals (a measure of social disadvantage).

Height was measured to 0.1 cm with a free standing Magnimeter stadiometer (Raven, Dunmow). Weights were recorded to 0.1 kg without shoes or jumpers. The mean of three triceps measurements was taken.⁴ Body mass index (weight (kg)/(height (m)²)) was calculated and converted to standard deviation scores using the revised 1990 reference standards⁵ and the Tanner Whitehouse (1975) standards for skinfold thickness.⁴ The following conventional cut-off points were applied: body mass index standard deviation score greater than 1.04 (85th centile) for overweight and greater than 1.64 (95th centile) for obesity. Using these definitions the expected percentages were 15% for overweight and 5% for obesity, relative to British children in 1990. Observed levels were compared with expected levels using ² goodness of fit test.

All but 21 children agreed to participate. Overall, 608 children were measured in 1996, 540 in 1997, and 499 in 1998 (some of whom were not measured in 1997). In addition 86 new children joined the study in 1997 and 1998. In total 694 children were measured, resulting in 1762 measurements.

The table shows the proportion of children with body mass index and triceps measurements above the 85th and 95th centiles according to age. A significant increase in the proportion of overweight and obese children was observed in those aged 9, 10, and 11 years.

	Comment

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A noticeable increase in the prevalence of obesity has been observed such that one in five 9 year olds and one in three 11 year old girls are overweight. We collected new data on measurements of the skinfold at the triceps. Given the increase in the extent of body mass index these measures were surprisingly not significantly greater than those expected from the 1975 standards. Anecdotal evidence suggests that the 1975 standards were based on overweight children (T Coles, personal communication), and this may prove to be the simple explanation. However, a larger study is required to establish new references. The latest British growth standards were developed in 1990, but less than a decade later it has become evident that these standards no longer reflect the distribution of weight in British schoolchildren.

The cause for concern is twofold. Firstly, cohort studies show that obesity may track from childhood to adulthood, where morbidity is very evident. Secondly, obesity in adolescence is directly associated with increased morbidity and mortality in adult life independent of adult body weight. This study lends further support to reports that levels of obesity in Britain are increasing at an appreciable rate in primary school children, that the measures of skinfold at the triceps need to be revalidated, and that this major public health issue needs urgently addressing in young children.

	Acknowledgments

   Contributors: MCJR was the principle investigator of the active programme promoting lifestyle education in school project. She conceived and designed the article, analysed and interpreted the data, and drafted the manuscript. She will act as guarantor for the paper. PS was the project manager of the active programme promoting lifestyle education in school project, analysed the raw data, discussed core ideas, and revised the article for intellectual content. JHB discussed the core ideas and edited the article. JW collected the anthropometric data and also discussed core ideas.

	Footnotes

Funding: This research was supported by a grant from NHS Northern and Yorkshire Region Research and Development Unit. The Castlemead Growth Programme 1993, a software package produced by Castlemead, was used to analyse the body mass index and triceps data.

Competing interests: JHB has received consultancy fees from Roche Pharmaceuticals.

This article is part of the BMJ's randomised controlled trial of open peer review. Documentation relating to the editorial decision making process is available on the BMJ's website

	References

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1.	Reilly JJ, Dorosty AR, Emmett PM. Prevalence of overweight and obesity in British children: cohort study. BMJ 1999; 319: 1039[Free Full Text].
2.	Reilly JJ, Dorosty AR. Epidemic of obesity in UK children. Lancet 1999; 354: 1874-1875[CrossRef][Medline].
3.	Sahota P, Rudolf MCJ, Dixey R, Hill AJ, Barth JH, Cade J. APPLES: a primary school based randomised controlled trial to reduce obesity risk factors. BMJ (in press).
4.	Tanner JM, Whitehouse RH. Revised standards for triceps and subscapular skinfolds in British children. Arch Dis Child 1975; 50: 142-145[Abstract/Free Full Text].
5.	Cole TJ, Freeman JV, Preece MA. Body mass index reference curves for the UK, 1990. Arch Dis Child 1995; 73: 25-29[Abstract/Free Full Text].

(Accepted 21 December 2000)