The arithmetic dilemma when defining thinness, overweight and obesity in stunted populations

Keywords: BMI, stunting, prevalence, thinness, obesity, misclassification, double burden of malnutrition

Abstract

Background: Critical cut-off values of BMI-for-age z-scores (BAZ) are used to define “thinness”, “overweight” and “obesity”, but the validity of these cut-off values needs to be questioned in populations that are shorter or taller than the reference. We hypothesized that the prevalence of thinness, overweight, and obesity depends on population height and performed a random simulation.

Methods: We created virtual child populations aged 2-10 years with normally distributed height expressed as height-for-age z-scores (HAZ) and weight expressed as weight-for-age z-score (WAZ), based on WHO growth standards and references, with a correlation r=0.7 between height and weight. We adjusted weight-for-height and calculated BAZ.

Results: BAZ depends on height and age. In short children (mean HAZ=-2 to HAZ=-3), the prevalence of thinness falls to less than 1% in the youngest and rises up to 10% (mean HAZ=-2) and up to 13% (mean HAZ=-3) at age 10 years. The prevalence of obesity rises to up to 7% in the shortest and youngest and falls close to zero at age 10. Short young children and tall older children are more prone to be misclassified as overweight.

Conclusions: The prevalence of thinness, overweight and obesity depends on height and age. The coexistence of being short and being overweight – currently referred to as “double burden of malnutrition” – needs consideration as to what extent this condition is a health issue or reflects calculation artefacts. The arithmetic dilemma particularly affects young children in short populations. We suggest abstaining from defining “thinness”, “overweight”, or “obesity” by BMI z-scores. Different states of under- and malnutrition should rather be classified by direct or indirect measures of body fat.

References

Akombi, B. J./Chitekwe, S./Sahle, B. W./Renzaho, A. M. N. (2019). Estimating the double burden of malnutrition among 595,975 children in 65 low- and middle-income countries: a meta-analysis of demographic and health surveys. International Journal of Environmental Research and Public Health 16 (16), E2886. https://doi.org/10.3390/ijerph16162886.

CDC (2015). Growth chart training | DNPAO | CDC. Available online at https://www.cdc.gov/nccdphp/dnpao/growthcharts/index.htm (accessed 3/21/2022).

Cole, T. J. (1990). The LMS method for constructing normalized growth standards. European Journal of Clinical Nutrition 44 (1), 45–60.

Cole, T. J./Lobstein, T. (2012). Extended international (IOTF) body mass index cut-offs for thinness, overweight and obesity. Pediatric Obesity 7 (4), 284–294. https://doi.org/10.1111/j.2047-6310.2012.00064.x.

de Onis, M./Lobstein, T. (2010). Defining obesity risk status in the general childhood population: Which cut-offs should we use? International Journal of Pediatric Obesity 5 (6), 458–460. https://doi.org/10.3109/17477161003615583.

Duggleby, S. L./Jackson, A. A./Godfrey, K. M./Robinson, S. M./Inskip, H. M. (2009). Cut-off points for anthropometric indices of adiposity: differential classification in a large population of young women. The British Journal of Nutrition 101 (3), 424–430. https://doi.org/10.1017/S0007114508012245.

Eveleth, P. B./Tanner, J. M. (1990). Worldwide variation in human growth. Cambridge, Cambridge University Press.

Fredriks, A. M./van Buuren, S./Burgmeijer, R. J./Meulmeester, J. F./Beuker, R. J./Brugman, E./Roede, M. J./Verloove-Vanhorick, S. P./Wit, J. M. (2000). Continuing positive secular growth change in the Netherlands 1955-1997. Pediatric Research 47 (3), 316–323. https://doi.org/10.1203/00006450-200003000-00006.

Goodreau, S. M./Handcock, M. S./Hunter, D. R./Butts, C. T./Morris, M. (2008). A statnet tutorial. Journal of Statistical Software 24 (1), 1–26. https://doi.org/10.18637/jss.v024.i09.

Guedes, D. P./Almeida, F. N./Neto, J. T. M./Maia, Maria de Fátima de M./Tolentino, T. M. (2013). Low body weight/thinness, overweight and obesity of children and adolescents from a Brazilian region of low economic status. Revista Paulista de Pediatria 31, 437–443. https://doi.org/10.1590/S0103-05822013000400004.

Hai, T. T./Bardosono, S./Wiradnyani, L. A. A./Hop, L. T./Ngan, H. T. D./Phuong, H. N. (2020). The optimal mid-upper-arm circumference cutoffs to screen severe acute malnutrition in Vietnamese children. AIMS Public Health 7 (1), 188–196. https://doi.org/10.3934/publichealth.2020016.

Handcock, M. S./Hunter, D. R./Butts, C. T./Goodreau, S. M./Morris, M. (2008). statnet: Software tools for the representation, visualization, analysis and simulation of network data. Journal of Statistical Software 24 (1), 1548–7660. https://doi.org/10.18637/jss.v024.i01.

Mumm, R./Hermanussen, M. (2021). A short note on the BMI and on secular changes in BMI. Human Biology and Public Health 2. https://doi.org/10.52905/hbph.v2.17.

NCD Risk Factor Collaboration (2017). Worldwide trends in body-mass index, underweight, overweight, and obesity from 1975 to 2016: a pooled analysis of 2416 population-based measurement studies in 128·9 million children, adolescents, and adults. Lancet 390 (10113), 2627–2642. https://doi.org/10.1016/S0140-6736(17)32129-3.

Ricardo, L. I. C./Gatica-Domínguez, G./Crochemore-Silva, I./Neves, P. A. R./dos Santos Vaz, J./Barros, A. J. D./Victora, C. G. (2021). Age patterns in overweight and wasting prevalence of under 5-year-old children from low- and middle-income countries. International Journal of Obesity, 1–6. https://doi.org/10.1038/s41366-021-00911-5.

Soetaert, K. (2021). plot3D: Plotting multi-dimensional data version 1.4 from CRAN. Available online at https://rdrr.io/cran/plot3D/ (accessed 9/28/2021).

Tanner, J. M. (1981). A history of the study of human growth. Cambridge, Cambridge University Press.

The R Foundation (2022). The R Foundation. Available online at https://www.r-project.org/foundation/ (accessed 8/18/2022).

UNICEF (2020). Malnutrition in children. Available online at https://data.unicef.org/topic/nutrition/malnutrition/ (accessed 10/10/2021).

Walker, R./Gurven, M./Hill, K./Migliano, A./Chagnon, N./de Souza, R./Djurovic, G./Hames, R./Hurtado, A. M./Kaplan, H./Kramer, K./Oliver, W. J./Valeggia, C./Yamauchi, T. (2006). Growth rates and life histories in twenty-two small-scale societies. American Journal of Human Biology 18 (3), 295–311. https://doi.org/10.1002/ajhb.20510.

WHO (2006). WHO child growth standards: length/height-for-age, weight-for-age, weight-for-length, weight-for-height and body mass index-for-age: methods and development. Available online at https://www.who.int/publications/i/item/924154693X (accessed 9/25/2021).

WHO (2016). The double burden of malnutrition: policy brief. Available online at https://apps.who.int/iris/handle/10665/255413 (accessed 8/19/2022).

WHO growth reference (2007). Growth reference data for 5-19 years. Available online at https://www.who.int/toolkits/growth-reference-data-for-5to19-years (accessed 8/19/2022).

WHO Multicentre Growth Reference Study Group (2006). WHO Child Growth Standards based on length/height, weight and age. Acta Paediatrica Suppl. 450, 76–85. https://doi.org/10.1111/j.1651-2227.2006.tb02378.x.

Zorlu, G. (2011). New WHO child growth standards catch on. Bulletin of the World Health Organization 89 (4), 250–251. https://doi.org/10.2471/BLT.11.040411.

Published
2022-08-24
How to Cite
Hermanussen, M., Novine, M., Scheffler, C., & Groth, D. (2022). The arithmetic dilemma when defining thinness, overweight and obesity in stunted populations. Human Biology and Public Health, 1. https://doi.org/10.52905/hbph2022.1.21
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Articles