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Rapid Responses: Rapid Responses published:
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Too early to ditch the fizz campaign
- J. Lennert Veerman, Jan J. Barendregt (11 October 2007)
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Intervention at what age, which method and how long?
- Urban Rosenqvist (14 October 2007)
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Why what works in Christchurch might not work here
- Helen Roberts, Philip Rose, Angela Harden, Ann Oakley,Jenny Woodman (21 October 2007)
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Obesity among young people in Mirpur, Pakistan
- Ikhlaq H. Din (25 October 2007)
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Unfeasible results at 12 months challenge the validity of findings concerning obesity prevention
- Russell M Viner, Timothy J Cole (2 November 2007)
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J. Lennert Veerman, Research Fellow UQ School of Population Health, Herston Road, Herston, QLD 4030, Australia, Jan J. Barendregt
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Dear Sir, James et al report that a school-based intervention that reduced children’s consumption of carbonated drinks and the prevalence of overweight was no longer effective two years after completion of the intervention (1). We believe that this conclusion is not warranted, for two reasons. The first reason is that the authors base their conclusions solely on the proportion of children with overweight. Indeed, this is was statistically significantly different between the intervention and the control groups at 12 months, and not at 3 years. However, we would argue that average values of BMI, Z-score and waist circumference are better outcome values to use for a population-targeted intervention such as the CHOPPS. Geoffrey Rose pointed out that numbers of overweight or obese individuals are merely those that fall above an arbitrary cut-off point (2). The distribution of BMI in populations can be reasonably well described by a lognormal curve, of which the average shifts to higher values as the obesity ‘epidemic’ progresses (3). Similarly, for Z-scores and waist circumference population distributions can be assumed. Table 1 makes clear that the changes in BMI, Z-score and waist circumference moved quite a bit towards significance: from p=0.36 to p=0.12, 0.60 to 0.06 and 0.81 to 0.25, respectively. Our conclusion would therefore be that the intervention did not have a significant effect on overweight after 12 months but that it is moving in the right direction. This is not surprising. Body mass accumulates. Suppose the children learnt to consume less carbonated drinks as a result of the intervention, and that they continue to apply this knowledge as the years pass. This would result in them putting on less weight every year, which after a number of years would become visible in their body mass. We would therefore advise James and colleagues to measure the children again in another couple of years – they may well find the desired statistically significant results. The second reason we think James et al’s conclusion is not warranted is because of trial characteristics. The trial was originally powered to detect differences in consumption of carbonated drinks, not proportion of overweight. Due to considerable loss-to-follow-up at three year power has further declined. In addition there were large differences at baseline: though not statistically significantly so, the intervention group had an average BMI, Z-score and waist circumference that was lower than that in the control group. Despite the randomisation process, we remain worried that, by chance or by selection, the intervention group might be less prone to overweight. In that case, any observed difference in the prevalence of overweight would not be (fully) attributable to the intervention. Childhood obesity and what to do about it is a huge problem, with so far very few solutions. In our opinion, James et al dismiss what looks like a promising result, based on an inappropriate outcome measure from an insufficiently powered and poorly randomised trial. References (1) James J, Thomas P, Kerr D. Preventing childhood obesity: two year follow-up results from the Christchurch obesity prevention programme in schools (CHOPPS). Bmj 2007. (2) Rose G. The Strategy of Preventive Medicine. Oxford: Oxford University Press, 1992. (3) Veerman JL, Barendregt JJ, van Beeck EF, Seidell JC, Mackenbach JP. Stemming the obesity epidemic: a tantalizing prospect. Obesity (Silver Spring) 2007;15(9):2365-70. Competing interests: None declared |
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Urban Rosenqvist, Professor em Uppsala university, dpt of Public Health and Caring Science, 751 85 Uppsala, Sweden
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In her recent thesis Dr Jiang Jiagxiong has worked obese children at different ages (1). Her results demonstrate that it is possible to reduce overweight. She has tested different methods and ages for intervention. Her results indicate that pre school children might be more receptive. Although her studies were carried out in Beijing, China, I think the results are well worth considering for other cultural settings. 1. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-7159 Competing interests: None declared |
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Helen Roberts, Profesor of Child Health Social Science Research Unit, Institute of Education, 18 Woburn Square, London WC1H ONR, Philip Rose, Angela Harden, Ann Oakley,Jenny Woodman
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Sir, We welcome the addition to the under-populated child public health trial literature of James et al’s obesity prevention study. From a scientific point of view, findings like these are just as valuable as those showing positive results. However, it is always disheartening when an intervention which appears plausible, is well designed, and is as well implemented as this one appears to have been, shows less than positive results. It seems to us that as well as building on traditional systematic review evidence and earlier succesful trials in new studies,as these authors have done, we also need to be more systematic in reviewing the views or ‘voice’ literature on children and young peoples’ views of these matters (1), and tease out contextual issues when interventions are implemented in different settings (2). The EPPI-Centre’s own review on children and healthy eating (3) for instance, found that children do not see it as their role to be interested in health; children do not see messages about future health as personally relevant or credible; fruit, vegetables and confectionery have very different meanings for children; children actively seek ways to exercise their own choices with regard to food; children value eating as a social occasion; and children see the contradiction between what is promoted in theory and what adults provide in practice. These issues may helpfully supplement the discussion provided by the authors and assist in informing the design of future trials in this area Helen Roberts, Professor of Child Health
1.Thomas J, Harden A, Oakley A, Oliver S, Sutcliffe K, Rees R, Brunton G, Kavanagh J (2004) Integrating qualitative research with trials in systematic reviews: an example from public health. British Medical Journal 328: 1010-1012. 2. Arai L, Roen K, Roberts H, Popay J (2005) It might work in Oklahoma but will it work in Oakhampton? What does the effectiveness literature on domestic smoke detectors tell us about context and implementation? Injury Prevention 11, 148-151 3. Thomas J, Sutcliffe K, Harden A, Oakley A, Oliver S, Rees R, Brunton G, Kavanagh J (2005) The barriers to, and the facilitators of, healthy eating among children: findings from a systematic review. In: Cameron N, Norgan N, Ellison G (eds) Childhood Obesity: Contemporary issues. New York: CRC Press, pages 223-250. ISBN: 0849328578 Competing interests: None declared |
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Ikhlaq H. Din, Independent Health Consultant BD7 3DN
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Although we have increasing amount of research on levels of obesity and outcomes in terms of diseases among young people in western countries (particularly among school children) and the 'best' ways of combating this. My research related to food consumption and physical activity among young people in Mirpur, Pakistan shows that similar trend is happening there also among the lower social-economic groups and this is partly based on increased financial resources among this group. Health centres and clinics in semi-urban areas play an important role in advising and raising awareness among all groups. The lack of appropriate health information (relating to food consumption and obesity) was found to be a major obstacle. Health centres and clinics in urban and particularly in rural areas play a crucial role in tackling this problem. Dr Ikhlaq Din ikhlaqdin@hotmail.co.uk Competing interests: None declared |
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Russell M Viner, Reader in Adolescent Health Institute of Child Health, University College London WC1N 3EH, Timothy J Cole
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Dear Sir We have concerns about the conclusions of the study by James et al, specifically regarding the impact of their Christchurch obesity prevention programme in school (CHOPPS) at 12 and 36 months.[1] The authors show that their invention produced a significant reduction in their primary outcome, progression in childhood overweight, at 12 months[2] but that this was not maintained at 36 months.[1] The proportion of overweight children (BMI ≥ 91st centile) in the control group rose from 20.6% at baseline to 28.5% 12 months later, while the rise in the intervention group from 17.4% to 18.7% was significantly smaller (p=0.01). We suggest that the rise in the control group is unfeasibly large for a representative population of 7-11 year olds. The fact that this proportion rose only a further 1.7% over the following 24 months (from 28.5% to 30.2%) supports this contention, and suggests that the control data were either in error, or that other factors were operating to increase BMI in a way not seen in the general population. This, we believe, invalidates the comparison with the intervention group. It is striking that BMI z-score and waist z-score in the control group changed very little between baseline and 12 months. Perhaps the only way to square this with the large rise in proportion overweight is to assume that the small changes in BMI caused a disparately large number of children to cross the overweight threshold. We conclude therefore that the findings of this study, particularly the claimed benefit of the intervention at 12 months, should be regarded with caution and that replication is needed. Yours sincerely Russell M Viner, Reader Timothy J Cole, Professor Institute of Child Health, University College London Reference List (1) James J, Thomas P, Kerr D. Preventing childhood obesity: two year follow-up results from the Christchurch obesity prevention programme in schools (CHOPPS). BMJ 2007; 335(7623):762. (2) James J, Thomas P, Cavan D, Kerr D. Preventing childhood obesity by reducing consumption of carbonated drinks: cluster randomised controlled trial. BMJ 2004; 328(7450):1237. Competing interests: None declared |
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