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School-based health interventions should be assessed with measures of fitness and fatness: comment on ‘Beyond the randomised controlled trial and BMI – evaluation of effectiveness of through-school nutrition and physical activity programmes’

Published online by Cambridge University Press:  12 May 2015

Jon Cornwall*
Affiliation:
Centre for Society, Governance and Science Faculty of Law University of OtagoPO Box 56, Dunedin, New Zealand
Lee Stoner
Affiliation:
School of Sport and ExerciseMassey UniversityWellington, New Zealand
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Abstract

Type
Letter to the Editor
Copyright
Copyright © The Authors 2015 

Madam

The commentary by Rush et al. promotes the time to run 550m test (T 550m) as an alternative outcome to BMI for assessing the ‘progress and effectiveness’ of school-based obesity interventions( Reference Rush, McLennan and Obolonkin 1 ). While the authors assert that a faster T 550m is ‘associated with improved nutrition and body composition’, we believe this to be an over-interpretation of the physiological importance of this test. Physiologically, the T 550m is a measure of ‘fitness’, whereas BMI is a measure of ‘fatness’. In adults, cardiometabolic disorders are more closely associated with fitness than fatness( Reference Fogelholm 2 ); however, in children the contributions of fatness and fitness to cardiometabolic risk factors are less clear: one study has reported that leanness in children is more important than fitness for predicating cardiometabolic risk profiles( Reference Moschonis, Mougios and Papandreou 3 ). As the authors discuss( Reference Rush, McLennan and Obolonkin 1 ), school-based health intervention research has produced mixed findings when the outcome is BMI. However, prior to dismissing the importance of ‘fatness’, the rubric used to judge this variable should first be scrutinized. It is well accepted that BMI is particularly poor at discriminating between lean mass and body fat, or type of adipose tissue( Reference Cepeda-Valery, Pressman and Figueredo 4 , Reference Stoner and Cornwall 5 ). The mixed findings reported using BMI do not necessarily mean that fatness is an unimportant measurement, but rather that ‘fatness’ is not being adequately assessed. Indeed, fatness is highly related to cardiometabolic pathology when superior assessments of fatness are collected( Reference Li and McDermott 6 ). While we agree that fitness is an important physiological outcome, fatness is likely associated with different risk factors to fitness and in this regard there remains an ongoing need to implement the use of measures superior to BMI. In particular, consideration should be given to equally simple-to-measure anthropometric indices, including waist circumference, waist-to-height ratio and waist-to-hip ratio, which take into consideration body fat distribution, especially central (abdominal) fat( Reference Cepeda-Valery, Pressman and Figueredo 4 , Reference Li and McDermott 6 ). If the T 550m is to be utilised as a research tool in children, then it should be compared with validated fitness assessment tools, not suggested as a replacement of a tool such as BMI that is used to assess fatness. In terms of cardiometabolic health the question of ‘fit’ or ‘fat’ is important, however it has not been well explored in children: school-based interventions should be assessing both physiological parameters to provide a more concise understanding of the nature of these variables in children’s cardiometabolic health.

Acknowledgements

Financial support: This work received no financial specific grant from any funding agency in the public, commercial or not-for-profit sectors. Conflict of interest: None. Authorship: J.C. and L.S. conceived the idea for the correspondence; J.C. and L.S. wrote and revised the correspondence.

References

1. Rush, E, McLennan, S, Obolonkin, V et al. (2015) Beyond the randomised controlled trial and BMI – evaluation of effectiveness of through-school nutrition and physical activity programmes (Invited Commentary). Public Health Nutr 18, 15781581.CrossRefGoogle Scholar
2. Fogelholm, M (2010) Physical activity, fitness and fatness: relations to mortality, morbidity and disease risk factors. A systematic review. Obes Rev 11, 202221.Google Scholar
3. Moschonis, G, Mougios, V, Papandreou, C et al. (2013) ‘Leaner and less fit’ children have a better cardiometabolic profile than their ‘heavier and more fit’ peers: The Healthy Growth Study. Nutr Metab Cardiovasc Dis 23, 10581065.Google Scholar
4. Cepeda-Valery, B, Pressman, GS, Figueredo, VM et al. (2011) Impact of obesity on total and cardiovascular mortality – fat or fiction? Nat Rev Cardiol 8, 233237.Google Scholar
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