A Thesis submitted to the Faculty of Health Sciences, University of the Witwatersrand,
Johannesburg, in ful lment of the requirements for the degree of Doctor of Philosophy
in Medicine
Johannesburg, South Africa 2017. / Background: The persistent burden of undernutrition, with increasing prevalence of
obesity and metabolic disease risk among children and adolescents, has become a global
public health problem. Research has shown that risk factors established in childhood and
adolescence may contribute to the development of non-communicable diseases (NCDs) in
adulthood. This is of particular concern in South Africa, given its rapid socio-economic,
political and epidemiological transitions. Research into the trends of nutrition transition
in rural children and adolescents, whose particular health needs have been under-served
and poorly delineated in the past, provides a unique opportunity to study the e ects of
rapid health transitions on development.
Aim: To determine the association of nutrition, body composition and metabolic disease
risk in rural South African children and adolescents.
Study design: Three cross-sectional studies were undertaken to address the overall aim
of this research. The speci c objectives of each study were: (1) to determine the association
of nutrition on body composition and metabolic disease risk in children and
adolescents; (2) to examine the associations between body mass index (BMI), disordered
eating attitude and body dissatisfaction in female adolescents, and descriptive attributes
assigned to silhouettes of di ering body habitus in male and female adolescents; and (3)
to investigate associations between diet and cardiovascular disease (CVD) risk factors in
adolescents.
Method: One cross-sectional study, 3 analyses were nested within the Agincourt Health
and Socio-demographic Surveillance System (HDSS) site, in the Bushbuckridge subdistrict,
Mpumalanga Province, South Africa. In 2009, a random sample of 600 children
and adolescents, from age groups 7 to 8 years, 11 to 12 years and 14 to 15 years, were
selected from 3489 children who had participated in a 2007 growth survey. These children
and adolescents had to have lived in Agincourt at least 80% of the time since birth or
since 1992, when enrolment into the Agincourt Health and Socio-Demographic Surveillance
System (HDSS) began. Height and weight were measured to determine BMI. Age
and sex-speci c cut-o s for underweight and overweight/obesity were determined using
those of the International Obesity Task Force. Body image satisfaction using Feel-Ideal
Discrepancy (FID) scores, Eating Attitudes Test-26 (EAT-26), perceptual female silhouettes
and pubertal assessment were collected through self-administered questionnaires.
Blood pressure (systolic (SBP) and diastolic (DBP)) was measured, fasting blood samv
ples were collected for the determination of glucose and lipids.
Waist to hip ratio cut-o s of (WHR) >0.85 for females, >0.90 for males, waist to height
ratio (WHtR) of >0.5 for both sexes, and waist circumference (WC) of >80 cm for females
and >94 cm for males were used to determine the risk of adiposity. For abnormal
lipids: high density lipoprotein cholesterol (HDL-C) cut-o s of >1.03 mmol/l, low density
lipoprotein-cholesterol (LDL-C) of >2.59 mmol/l, triglycerides (TGs) of >1.7 mmol/l and
total cholesterol (TC) of >5.17 mmol/l were used. Pre-hypertension prevalence was computed
using the average of 2 readings of SBP or DBP, being >90th but <95th percentile for
age, sex and height. Dietary intake was assessed using semi-quantitative food frequency
questionnaire. T-test and ANOVAs for normally distributed data and Wilcoxon-Mann-
Whitney test was used to determine signi cant di erences by sex and by pubertal stages
for EAT-26 and EAT-26 sub-scores. Chi square tests were done to determine signi cant
associations between the categorical variables. Bivariate linear regression was employed
to test associations and signi cant tests were set at the p<0.05 level.
Results: Study component (1): Stunting levels were higher in the boys than in the girls
in mid to late childhood and combined overweight and obesity prevalence was higher in
girls than in boys. The girls' BMI was signi cantly greater at ages 11 and 12 years than
that of the boys [girls: 18 3.4, 95% con dence interval (CI): 17.33- 18.69; boys: 17
2, 95% CI: 16.46-17.25; p-value 0.004] and at ages 14-15 years (girls: 22 4.1, 95%
CI: 20.82-22.47; boys: 19 2.4, 95% CI: 18.39-19.38; p-value < 0.001). Prehypertension
(de ned as < 90th centile for age, sex and height) was higher in girls (15%) than boys
(10%). Further, impaired fasting glucose was detected in 5.3% of girls and 5% of boys.
High-density lipoprotein cholesterol (>1.03 mmol/l) concentrations were observed in 12%
of the girls and 0.7% of the boys, which is indicative of cardiometabolic risk.
Study component (2): The prevalence of overweight and obesity was higher in girls than
boys in early and mid to post pubertal stages. The majority (83.5%) of the girls reported
body image dissatisfaction (a desire to be thinner or fatter). The girls who wanted to be
fatter had a signi cantly higher BMI than the girls who wanted to be thinner (p=0.001).
There were no di erences in EAT-26 score between pubertal groups, or between boys and
girls within the two pubertal groups. The majority of the boys and the girls in both
pubertal groups perceived the underweight silhouettes to be \unhappy" and \weak" and
the majority of girls in both pubertal groups perceived the normal silhouettes to be the
\best".
Study component (3): Added sugar and sweets contributed 10% and maize meal and
vi
bread contributed 7.2% to the total number of food items consumed respectively. Girls
had higher intakes of total fat, saturated fat and cholesterol after adjusting for dietary
energy intake and age (all p<0.001). The prevalence of combined overweight and obesity
was 13.8% in girls and 3.1% in boys (p<0.001). In addition, indicators of adiposity were
higher in females, abnormal waist circumference (WC) (6.7%), waist to hip ratio (WHR)
(22.0%) and waist to height ratio (WHtR) (18.0%), compared to males, (0%), (3.1%)
and (6.2%) respectively (all p<0.001). Girls had higher low-density lipoprotein (LDL)
(12(9.3%) vs. 3(2.3%), p=0.01), total cholesterol (17(12.7%) vs. 5(3.5%), p<0.001) and
were more pre-hypertensive (28(15.3%) vs.15(8.4%), p=0.04) than the boys. Furthermore,
the bivariate associations between dietary intakes (total energy, total carbohydrate
(CHO), total dietary fat and saturated fat) and anthropometric indices (BMI and WC)
showed that body mass index (BMI) was associated with total energy (p=0.05) and BMI
and WC were associated with total fat (p=0.01, p=0.03) and saturated fat (p<0.001,
p=0.02) in females respectively.
Conclusions: In conclusion, this thesis highlights that girls in rural South Africa had a
higher prevalence of combined overweight and obesity than did boys, stunting was more
prevalent amongst boys than girls in mid to late childhood and metabolic risk factors that
were associated with adiposity, and linked to diet, were higher in girls than in boys. This
study has provided useful information for targeting critical health promotion intervention
programmes to optimise child nutrition as part of a noncommunicable disease preventative
strategy, especially, in remote areas in rapidly transitioning South Africa. / LG2018
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:wits/oai:wiredspace.wits.ac.za:10539/24736 |
| Date | January 2017 |
| Creators | Pedro, Titilola Minsturat |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | English |
| Type | Thesis |
| Format | application/pdf |
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