Abstract
Objectives: While available data exist on total body fat of rural South African children, as measured by body mass index, little is known concerning the abdominal obesity of rural South African children. The aim of this study was to determine the prevalence of abdominal obesity among rural South African children.
Methods : Participants involved 1 172 rural black school children (541 boys and 631 girls) aged 10−16 years, residing in Mankweng and Toronto, both rural black settlements in Capricorn district, Limpopo province, South Africa. Height, weight and waist circumference were measured using standard techniques. Waist-to-height ratio (WHtR) was calculated. A WHtR ≤ 0.50 was used to determine abdominal obesity. Results were analysed using student t-test and Chi-squared statistics, with a p-value of < 0.05.
Results : Waist-to-height ratio showed inconsistent results in both sexes and across age groups, with no significant differences among boys and girls in all age groups. The proportion of boys with a WHtR ≥ 0.5 was 69 (12.8%), while girls were 92 (14.6%). The highest proportion of WHtR occurs at age 11 in boys, while this proportionality increases with age in girls, peaking at ages 14-16 years. Overall, 161 (13.7%) children had central obesity.
Conclusions : This study indicates that abdominal obesity as measured by WHtR is prevalent among rural black South African children. The prevalence of WHtR ≥ 0.5 (13.7%) among the children is worrisome, as its signals the presence of obesity-related problems and the likely susceptibility of these sample children to future health risks. Therefore, interventions strategies are needed to reduce central obesity among children.
Key Words: Abdominal obesity, Waist-to-height ratio, Rural children
INTRODUCTION
The importance of total body fat and distribution is a major risk factor for both adults and children.1 It is reported that the incidence of diabetes, atherosclerosis and sudden cardiac death is high among obese persons, but metabolic and cardiovascular adverse effects are even more significant when obesity is centered around the abdomen.2 Therefore, early identification and treatment of children with central obesity is essential in order to plan appropriate remedial strategies for their health. Thus, information on abdominal obesity is relevant judging from both an epidemiological and clinical viewpoint.
Several studies3-7 have reported a high prevalence of overweight and obesity among South African children. A meta-analytical study8 investigating the prevalence and intrinsic patterns of childhood overweight and obesity in South Africa covering 1998-2008, indicated that the high levels of overweight and obesity among South African children, occurs predominantly in the urban settings. The review also indicated that the trend in the prevalence of overweight and obesity in South African children is patterned along gender, race, age and socio-demographic and socio-economic factors.
Some studies3-5 have confirmed the occurrence of total obesity as measured by BMI among rural South African children. However, little is known concerning the prevalence of abdominal obesity among rural South African children. Only few studies6,9,10 have assessed the prevalence of abdominal obesity among South African children, especially among rural children. As such, whether abdominal obesity is prevalent among rural South African children is only speculative.
Although other precise methods of measuring abdominal obesity such as computed tomography, nuclear magnetic resonance imaging are available, few population studies using these methods exists, primarily due to its high operational cost. In this regards, anthropometric measures appears to be a good alternative for the diagnosis of abdominal obesity.11 Therefore, the purpose of this study was to assess abdominal obesity in rural South African residing in Mankweng and Toronto, Limpopo province, using the anthropometric index of waist-height-ratio (WHtR). This anthropometric index has been used by several researchers to evaluate abdominal obesity among children12-17 and is known to correlate well with cardiovascular disease risk factors in children and adolescents.17-19
The present study was designed to screen for abdominal obesity among rural South African children in Mankweng and Toronto regions, using WHtR.
METHODS
A stratified random sampling of 1172 (541 boys and 631 girls) children aged 10-16 years, attending seven primary schools in Mankweng and Toronto, both rural settlements in Capricorn district, Limpopo province, South Africa, participated in the study. Procedures used for sampling and collection of anthropometric data have been reported in detail elsewhere.5 The Central Higher Degrees Committee of Tshwane University of Technology, Pretoria, South Africa, and other relevant provincial regulatory authorities granted ethics approval for the research to be carried out. An information leaflet and informed consent form were administered to the head teachers, pupils and their parents or guardians who consented that the study be carried out.
Height, weight and waist circumference were measured using standard techniques.20 Waist-to-height ratio was calculated by dividing waist circumference (in cm) by stature (in cm). A WHtR ≤ 0.50 was used to determine abdominal obesity.21 Results were analysed using student t-test and Chi-squared statistics, with a p-value of < 0.05.
RESULTS
Shown in Table-I are the anthropometric measurements of the participants stratified by gender. The mean age of the participants was 12.3 ± 1.2 (boys 12.5 ± 1.3; girls 12.2 ± 1.2). Girls had significantly higher mean values in all the anthropometric variables compared to boys. A total of 161 (13.7%) children had central obesity as measured by WHtR. There was no significant (p = 0.157; p ≥ 0.05) difference in the mean value of WHtR between boys and girls. Waist-to-height ratio showed inconsistent results in both sexes and across age groups, with no significant differences among boys and girls in all age groups (Table-II). The proportion of boys with a WHtR ≥ 0.5 was 69 (12.8%), while girls were 92 (14.6%). The highest proportion of WHtR occurs at age 11 in boys, while this proportionality increases with age in girls, peaking at ages 14-16 years (Table-III).
Table-I.
Anthropometric measurements of the participants according to gender
| Boys (n = 541) | Girls (n =631) | Combined (n = 1172) | p-value | |
|---|---|---|---|---|
| Variables | Mean ± SD | Mean ± SD | Mean ± SD | |
| Height (cm) | 140.5 ± 13.6 | 143.2 ± 12.2 | 141.9 ± 12.9 | 0.001* |
| Body weight (kg) | 40.5 ± 9.9 | 43.6 ± 10.8 | 42.1 ±10.5 | 0.001* |
| Waist (minimum) (cm) | 59.8 ± 9.0 | 61.9 ± 9.5 | 7.0 ± 6.1 | 0.001* |
| Waist-to-height ratio | 0.45 ± 0.1 | 0.47 ± 0.1 | 0.44 ± 0.1 | 0.002* |
*Statistically significant (p ≤ 0.05)
Table-II.
Waist-to-height ratio of South African children according to age groups
| Waist-to-height ratio | |||||
|---|---|---|---|---|---|
| Age (years) | Boys | Girls | Boys (Mean ± SD) | Girls (Mean ± SD) | p-value |
| 10 | 26 | 42 | 0.43±0.05 | 0.43±0.07 | 0.773 |
| 11 | 110 | 147 | 0.44±0.07 | 0.43±0.08 | 0.463 |
| 12 | 150 | 162 | 0.43±0.06 | 0.44±0.06 | 0.588 |
| 13 | 133 | 194 | 0.42±0.07 | 0.44±0.06 | 0.095 |
| 14-16 | 122 | 86 | 0.42±0.06 | 0.43±0.07 | 0.165 |
| Total | 541 | 631 | 0.43±0.06 | 0.43±0.01 | 0.157 |
*Statistically significant (p ≤ 0.05); CI = Confidence Interval
Table-III.
Percentage of children with a WHtR at 0.5 or above cut-off point
| WHtR ≥0.5 | ||
|---|---|---|
| Age (years) | n | % |
| Boys | ||
| 10 | 4 | 15.4 |
| 11 | 20 | 18.2 |
| 12 | 25 | 16.7 |
| 13 | 14 | 10.5 |
| 14-16 | 6 | 4.9 |
| Total | 69 | 12.8 |
| Girls | ||
| 10 | 5 | 11.9 |
| 11 | 19 | 12.9 |
| 12 | 26 | 16.0 |
| 13 | 31 | 16.0 |
| 14-16 | 11 | 12.8 |
| Total | 92 | 14.6 |
| Boys/ Girls | 161 | 13.7 |
n = number of sample; % = percentage; WHtR = waist-to-height ratio
DISCUSSION
The WHtR is a valid method for assessing excessive amount of upper body fat that poses a risk to health22 with a simple message: keep your waist circumference to less than half your height’.15 This anthropometric index is easy and inexpensive can be used in laboratory and field settings. The WHtR indicator assumes that individuals with a certain anthropometric measure of fat patterning would have the same degree of fat regardless of their age, race, or gender. Also, WHtR has the advantage of better measurement of fat distribution in different ages and statures.23 This anthropometric index is not extensively studied in South African children, especially in rural children.
This study shows that the proportion of children with a WHtR ≥ 0.5 exists in both genders and in all age groups. The proportionality of WHtR ≥ 0.5 is higher in girls (14.6%) compared to boys (12.8%). Similarly, among one to 20 years black South African rural children, 10% of adolescents are reported to have WHtR ≥ 0.5, with a significantly higher proportion of girls (15.0%) than boys (3.0%).23 In Naude, Kruger and Pienaar’s24 study involving black South African adolescents, girls (3.5%) had WHtR ≥ 0.5, whereas none of the boys exhibited a WHtR ≥ 0.5. The figures of WHtR ≥ 0.5 (13.7%) found among rural children in these regions is unexpected and disturbing from a rural setting where lifestyles and other life habits are supposed to be different from those of urban setting. Decreased physical activities, sedentary lifestyles, altered eating patterns, and increased fat content of the diet among the children could be possible reasons for their high fat deposition. However, the present study did not evaluate these factors, which would have permitted further inquiry in this regard. Notwithstanding, the present findings appear to suggest that rural life does not necessarily encompass physically demanding tasks anymore25 and may be a factor in the prevalence of abdominal obesity in rural areas. Disturbingly, abdominal obesity is known to be associated with cardiovascular and metabolic2,7,18,19 disease risk factors in children and adolescents. Therefore, the future health of the children might be jeopardised. This indicates the need for interventions to reduce central obesity in all school populations and intensive community-based efforts to prevent it beginning very early in life.
The results of this study need to be interpreted with the understanding that the study is limited in several aspects. It is appropriate to assume that the sampled population represents the adolescent children in Mankweng and Toronto, but far from being a good sample at the provincial or the national level. Given the area and size of the sample, one must be very careful in generalising the findings obtained in this study. Also, the cross-sectional nature of the study limits inferences about causality and its direction.5
Ideally, abdominal obesity could be assessed using criterion measures such as computed tomography, nuclear magnetic resonance imaging. However, the use of these methods has limited applicability when screening larger sample sizes such as this, especially in developing countries like South Africa, largely because it is expensive, unavailable and time-consuming.6 In its place, measurements of anthropometry (height and waist circumference) were taken to screen for central fat pattern in group of South African rural children living in Mankweng and Toronto regions.
The strength of this study is based on the fact that it was conducted using a fairly large sample of rural black school children. This therefore, provides the opportunity to collect information in an understudied region that can be compared with results of very few previous studies carried out in South Africa concerning abdominal obesity using the same anthropometric index6,23,24 although with varying methodological and geographical settings.
CONCLUSION
The present study did not seek to determine the aetiology of abdominal obesity development in children, but to examine the prevalence of abdominal obesity among the children using the WHtR index. The analysis indicate that abdominal obesity is prevalent among rural black South African children in Mankweng and Toronto settlements. The prevalence of WHtR ≥ 0.5 (13.7%) among the children is worrisome, and typifies the presence of obesity-related problems and indicates the possibility of the children been susceptible to future health risks. Therefore, interventions strategies are warranted to reduce central obesity among children.
References
- 1.Conoy D, Boekholdt SM, Wareham N, Luben R, Welch A, Bingham S, et al. Body fat distribution and risk of coronary heart disease in men and women in the European Prospective Investigation into Cancer and Nutrition in Norfolk cohort: A population-based prospective study. Circulation. 2007;116:2933–2943. doi: 10.1161/CIRCULATIONAHA.106.673756. [DOI] [PubMed] [Google Scholar]
- 2.Krekoukia M, Nassis GP, Psarra G, Skenderi K, Chrousos GP, Sidossis LS. Elevated total and central adiposity and low physical activity are associated with insulin resistance in children. Metab Clin Exp. 2007;56:206–213. doi: 10.1016/j.metabol.2006.09.014. [DOI] [PubMed] [Google Scholar]
- 3.Monyeki KD, Van Lenthe FJ, Steyn NP. Obesity: does it occur in African children in a rural community in South Africa. Int J Epidemiol. 1999;28:287–292. doi: 10.1093/ije/28.2.287. [DOI] [PubMed] [Google Scholar]
- 4.Amusa LO, Goon DT, Adeniran SA, Mbhenyane XG. Does obesity occur in African children in a rural community? Afr J Phy Health Edu Recre Dance. 2011;(Supplement 2:1):212–221. [Google Scholar]
- 5.Toriola AL, Moselakgomo VK, Shaw BS, Goon DT. Prevalence of overweight, obesity and underweight in rural black African children. S Afr J Clin Nutr. 2012;25:57–61. [Google Scholar]
- 6.Goon DT, Toriola AL, Shaw BS, Amusa LO. Centripetal fat patterning in South African children. Pak J Med Sci. 2011;27:832–836. [Google Scholar]
- 7.Kruger R, Kruger HS, Maclntyre UE. The determinants of overweight and obesity among 10-to 15-year-old schoolchildren in the North west Province, South Africa-the THUSA BANA (Transition and Health during Urbanisation of South Africans: BANA, children) study. Public Health Nutr. 2005;9:351–358. doi: 10.1079/phn2006849. [DOI] [PubMed] [Google Scholar]
- 8.Du Toit D, van der Walt JL. Childhood overweight and obesity patterns in South Africa: a review. Afr J Phys Health Edu Recre Dance. 2009;15:15–31. [Google Scholar]
- 9.Cameron N, Johnston FE, Kgamphe JS, Lunz B. Body fat patterning in rural South African black children. Am J Hum Biol. 1992;4:353–364. doi: 10.1002/ajhb.1310040311. [DOI] [PubMed] [Google Scholar]
- 10.Monyeki MA, Kemper HCG, Makgae PJ. The association of fat patterning with blood pressure in rural South African children: The Ellisras Longitudinal Growth and Health Study. Int J Epidemiol. 2005;10:1–7. doi: 10.1093/ije/dyi219. [DOI] [PubMed] [Google Scholar]
- 11.Pitanga F. Anthropometry for the assessment of abdominal obesity and coronary risk. Rev Bras Cineathropom Desempenho Hum. 2011;13:238–241. [Google Scholar]
- 12.Goon DT, Toriola AL, Shaw BS, Shaw I, Amusa LO, de Ridder JH, et al. Centripetal fat patterning in Nigerian children. Afr J Phy Health Edu Recrea Dance. 2009;15:668–677. [Google Scholar]
- 13.Sung RYT, So HK, Choi KC, Nelson EAS, Li AM, Yin JAT, et al. Waist circumference and waist-to-height ratio of Hong Kong Chinese children. BMC Public Health. 2008;8 doi: 10.1186/1471-2458-8-324. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 14.Nambiar S, Truby H, Abbott RA, Davies PSW. Validating the waist-height ratio and developing centiles for use amongst children and adolescents. Acta Pediatr. 2009;98:148–152. doi: 10.1111/j.1651-2227.2008.01050.x. [DOI] [PubMed] [Google Scholar]
- 15.McCarthy HD, Ashwell M. A study of central fatness using waist-to-height ratios in UK children and adolescents over two decades supports the simple message-keep your waist circumference to less than half your height. Int J Obes. 2006;30:988–992. doi: 10.1038/sj.ijo.0803226. [DOI] [PubMed] [Google Scholar]
- 16.Ashwell M, Hsieh SD. Six reasons why the waist to height ratio is a rapid and effective global indicator for health risks of obesity and how its use could simplify the international public health message on obesity. Int J Food Sci Nutr. 2005;56:303–307. doi: 10.1080/09637480500195066. [DOI] [PubMed] [Google Scholar]
- 17.Freedman DS, Khan HS, Mei Z, Strawn LMG, Dietz WH, Srinivasan SR. Relation of body mass index and waist-to-height ratio to cardiovascular disease risk factors in children and adolescents: the Bogalusa Heart Study. Am J Clin Nutr. 2007;86:33–40. doi: 10.1093/ajcn/86.1.33. [DOI] [PubMed] [Google Scholar]
- 18.Meininger JC, Brosnan CA, Eissa MA, Nguyen TQ, Reyes LR, Upchurch SL, et al. Overweight and central adiposity in school-age children and links with hypertension. J Paediatri Nurs. 2010;25:119–125. doi: 10.1016/j.pedn.2008.09.003. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 19.Campagnolo PD, Hoffman DJ, Vitolo MR. Waist-to-height as a screening tool for children with risk factors for cardiovascular disease. Ann Hum Biol. 2011;38:265–270. doi: 10.3109/03014460.2010.526147. [DOI] [PubMed] [Google Scholar]
- 20.Marfell-Jones M, Olds T, Stew A, Carter L. International standards for anthropometric assessment. Australia: The International Society for the Advancement of Kinanthropometry; 2006. [Google Scholar]
- 21.Ashwell M, Hsieh SD. Six reasons why the waist to height ratio is a rapid and effective global indicator for health risks of obesity and how its use could simplify the international public health message on obesity. Int J Food Sci Nutr. 2005;56:303–307. doi: 10.1080/09637480500195066. [DOI] [PubMed] [Google Scholar]
- 22.Goon DT. Abdominal body fatness among Nigerian women: a study on the anthropometric index of waist-to-stature ratio. Pak J Med Sci. 2010;26:577–580. [Google Scholar]
- 23.Kimani-Murage EW, Kahn K, Pettifor JM, Tollman SM, Dunger DB, Gomez-Olive XF, et al. The prevalence of stunting, overweight and obesity, and metabolic disease risk in rural South African children. BMC Public Health. 2010;10 doi: 10.1186/1471-2458-10-158. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 24.Naude D, Kruger HS, Pienaar AE. Differences in body composition, body proportions and timing of puberty between stunted and non-stunted adolescents. Afr J Phys Health Edu Recrea Dance. 2009;15:678–689. [Google Scholar]
- 25.Wang Y. Cross - sectional comparison of childhood obesity: the epidemic and relationship between obesity and socio - economic status. Int J Epidem. 2001;30:1129–1136. doi: 10.1093/ije/30.5.1129. [DOI] [PubMed] [Google Scholar]