Herculina S. Kruger

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

AIM To investigate the determinants of overweight and obesity among 10- to 15-year-old schoolchildren in a population in the transitional phase in the North West Province of South Africa. METHODS A cross-sectional survey was used to investigate weight status (anthropometric indicators) and determinants of overweight/obesity including dietary intake, physical activity and socio-economic status. A single, random sample (n=1257), stratified for gender, type of school and ethnic group, was used. Data were collected on demographics, family circumstances, habitual physical activity, dietary intake and anthropometry to evaluate weight status and body fat content. One-way analysis of variance, the generalised linear models procedure of SAS and the Tukey post hoc honest significant difference test were used to analyse the data. RESULTS Few children were overweight or obese (7.8%) according to International Obesity Task Force (IOTF) standards (body mass index (BMI)-for-age). These standards were compared with other accepted standard values. Both Coles IOTF/BMI-for-age standard and the sum of skinfold thicknesses standard classified normal-weight status similarly at a level of 92% (P<0.01) and were found to be useful in determining overweight/obesity. The prevalence rate was higher in females and white children, and was more apparent in urban areas, smaller households and children of parents with low- or high-income occupations. Boys and pre-menarcheal girls had mean body fat percentage in the normal/optimal range, whereas that of post-menarcheal girls was moderately high. Few variables showed a significant association with high body fat percentage: in boys, only the number of members in the household and physical activity levels over the weekend; in girls, only age. The overweight/obese boys mostly lived in smaller households, and the overweight/obese post-menarcheal girls were most inactive on both weekdays and weekends, and more overweight with increasing age. CONCLUSION Smaller households, inactivity and increasing age for girls were found to be determinants that influence the development of overweight/obesity, while female gender and age post-menarche were identified as determinants of higher body fat content. For overweight/obesity prevention, the focus should be on pre-menarcheal girls, aged 10-13 years, using these determinants to identify overweight/obesity risk. Preventive programmes should aim to increase the physical activity of children to improve their current and future weight status.

An epidemiological study of hypertension and its determinants in a population in transition: the THUSA study

Background: Many black persons in South Africa have been subjected to urbanisation and urbanisation has led to a significant increase in diseases of lifestyle. The determinants of hypertension in a population in transition have not been well-defined and there is a pressing need for observational epidemiological studies as well as randomised-controlled trials in populations from Africa. The aim of this study was to investigate the association between blood pressure and factors known to contribute to hypertension.Methods: The study sample consisted mainly of Setswana speaking people, divided into different levels (strata) of urbanisation, namely stratum 1 (rural) to stratum 5 (urbanised). A total of 1821 black subjects, which included 1040 woman, were recruited and randomly selected from 37 sites from the four geographical quarters of the North West Province of South Africa. The following questionnaires were used: demographic, anthropometric, quantitative food frequency, physical activity and scales to measure psychosocial variables. Biochemical analysis (standardised methods) were done on the serum and plasma of the subjects and the blood pressure was measured with a sphygmo- manometer.Results: Of the total sample, 22.8% of the subjects had systolic and 20.7% diastolic blood pressures above 140/90 mm Hg. Males and females from stratum 3 showed the highest rate of hypertension (32.9% systolic and 25.1% diastolic) and stratum 5 the lowest. Blood pressure correlated positively with age, level of urbanisation, WHR (waist:hip ratio) and smoking. In the woman the diastolic blood pressure correlated the best with body mass index (BMI), serum triglycerides, total serum cholesterol, low-density lipoprotein (LDL) cholesterol and s-GGT. Coping strategies, experience of social support, cultural aspects and affect balance are related to blood pressure, especially in the case of women.Conclusions: It seems that factors associated with urbanisation are related to the manifestation of hypertension in black people of the North West Province, given the highest mean blood pressure in people living in informal settlements, where most newcomers to the urban areas live.

Dietary intakes of an African population in different stages of transition in the North West Province, South Africa: the THUSA study

This community based, cross-sectional study describes the effects of urbanization on the food intakes of the African population of the North West Province, South Africa. Dietary intakes of 1751 apparently healthy adults, stratified according to gender and stratum of urbanization were assessed using a validated quantitative food frequency questionnaire (QFFQ). Mean energy and protein intakes for all strata were adequate. Mean intakes of micronutrients were low in comparison to reference standards. Mean energy distribution was 65% carbohydrate, 12% protein and 22% fat for the rural, farm, informal settlement and middle class urban strata and 57%, 13% and 31% for the upper class urban strata. Intakes of the staple, maize meal, decreased between the urban middle and upper class strata. Fruit and vegetable consumption was low throughout the sample. Food intakes showed a shift from the traditional high carbohydrate low fat diet to a diet associated with noncommunicable diseases.

Obesity in African women in the North West Province, South Africa is associated with an increased risk of non-communicable diseases: the THUSA study

The objective of the present study was to assess the relationship between anthropometric measurements and risk factors for non-communicable diseases (NCD) in South African black women. A cross-sectional sample of 1040 apparently healthy black female volunteers, 15-70 years old, was recruited from thirty-seven randomly selected sites in the North West Province, stratified according to level of urbanisation. We analysed the association between BMI, waist:hip (WHR), waist circumference (WC) and skinfold measurements and the following risk factors for NCD: blood pressure, serum lipids, fasting serum glucose and insulin and plasma fibrinogen, by using age-adjusted correlation analyses and stepwise regression analysis. Of the subjects, 28.6 % were obese (BMI>30). After adjustment for age and smoking status, BMI correlated significantly with diastolic blood pressure (r 0.21, P=0.037), serum triacylglycerols (TG) (r 0.30, P=0.003), fasting glucose (r 0.29, P=0.005) and log fasting insulin (r 0.24, P=0.02). There was a significant negative correlation between BMI and HDL-cholesterol (r -0.38, P<0.001). Similar but stronger correlations were found between both WC and WHR and these risk factors. Together with age, WC was a significant predictor of TG, HDL-cholesterol and fasting glucose in regression analysis, while subscapular skinfold was a significant predictor of diastolic blood pressure and fasting glucose concentration. Triceps skinfold was a significant predictor of total serum cholesterol, LDL-cholesterol, plasma fibrinogen and the insulin sensitivity index. Measures of obesity, particularly WC, are associated with the risk for NCD in black South African women, in which a high rate of obesity has been found.

Factor analysis of possible risks for hypertension in a black South African population

To date only a small number of studies have investigated the pattern of associations within a set of hypertension risks. The objective of this study was therefore to examine the interrelation of main hypertension risks in an African population by using factor analysis in order to detect underlying risk patterns. Subjects aged 16–70 years (N=963) were recruited from 37 randomly selected sites throughout the North West Province during 1996–1998. Exclusion criteria were pregnancy, lactation, casual visitors, drunkenness and treatment for chronic diseases, such as hypertension. Subjects with blood pressures exceeding 140/90 mmHg were classified as hypertensive. Children aged 10–15 years were also recruited from 30 randomly selected schools during 2000–2001 (N=694). Children were classified as hypertensive when an average systolic or diastolic blood pressure greater than or equal to the 90th percentile for age and sex was encountered, while correcting for height. The following hypertension risks were measured: urbanisation, obesity, plasma fibrinogen, lipids, insulin, serum gamma glutamyl-transferase, dietary intake, smoking and alcohol consumption.From 23 risks the factor analysis disclosed five factors that explained 56.2% of the variance in the male and 43.5% of the variance in the female group: an urban malnutritional phenomenon, the metabolic syndrome X, a hypercholesterolaemic and obesity complex, an alcoholic hypertriglyceridaemia, and central and peripheral cardiovascular hypertensive effects. In conclusion, South Africans migrating from rural to urban areas adapt to a new lifestyle with numerous risks, resulting in conditions like malnutrition, the metabolic syndrome X, dyslipidaemia, alcoholism, obesity and increased peripheral vascular resistance. For successful prevention of hypertension in a population in transition, a whole risk pattern should be corrected, rather than an individual risk by implementing lifestyle modification programmes.

Habitual physical activity and body composition of black township adolescents residing in the North West Province, South Africa

OBJECTIVE It is known that stunting and obesity affect a large proportion of children in the world, and these can be affected by the physical activity levels of the children. In the present study, we evaluated the association between physical activity, physical development and body composition in black adolescent children. DESIGN Cross-sectional study. SETTING Black township schools in the North West Province, South Africa. METHODS Three-hundred and thirteen grade 8 children were included in the Physical Activity in Youth study. Anthropometric measurements, body composition measures and maturity level as assessed by Tanner stages were determined in these children. In addition, Previous Day Physical Activity Recall questionnaires were administered on the children to record the various activities they undertake daily. RESULTS The demographic characteristics of the children showed a high level of homogeneity. A high prevalence of stunting (16.3%) was observed in the children, which was higher in boys than in girls (21.6 vs. 12.3%). Also prevalent was overweight/obesity (8.6%), but this was higher in girls than in boys (13.4 vs. 1.6%). The children also showed a reduction in levels of physical activity with advancement in maturity; furthermore, boys showed a more central form of fat deposition whilst girls showed more gynoid deposition. CONCLUSIONS The study revealed that physical activity plays a role in determining body composition, and further indicated that physical activity is associated with favourable body composition measures. Children who were more active were likely to have less fat deposits.

Dietary risk markers that contribute to the aetiology of hypertension in black South African children: the THUSA BANA study

Although clinical hypertension occurs less frequently in children than in adults, ample evidence supports the concept that the roots of essential hypertension extend back to childhood. Since little is available in the literature on causal dietary factors of hypertension in children, this study hypothesised that certain dietary factors can be identified as risk markers that might contribute to the aetiology of hypertension in black children. Children aged 10–15 years were randomly selected from 30 schools in the North West Province from 2000 to 2001. These children comprised 321 black males and 373 females from rural to urbanised communities, of which 40 male and 79 female subjects were identified with high-normal to hypertensive blood pressure. Blood pressure was measured with a Finapres apparatus and data were analysed with the Fast Modelflo software program to provide systolic, diastolic and mean blood pressure. A 24-h dietary recall questionnaire and weight and height measurements were taken. In a stepwise regression analysis, the following variables were significantly associated (P⩽0.05) with blood pressure parameters of hypertensive males: biotin, folic acid, pantothenic acid, zinc and magnesium. Energy, biotin and vitamin A intakes were significantly associated with blood pressure parameters of hypertensive females. No significant dietary markers were indicated for any of the normotensive groups. Dietary intakes of all of these nutrients were well below the dietary reference intakes. In conclusion, the dietary results coupled with the cardiovascular parameters of this study identified folic acid and biotin as risk markers that could contribute to the aetiology of hypertension in black persons. The low intakes of these nutrients, among others, is a matter of serious concern, as is the increasing tendency towards urbanisation.

Evaluation of waist-to-height ratio to predict 5 year cardiometabolic risk in sub-Saharan African adults

BACKGROUND AND AIMS Simple, low-cost central obesity measures may help identify individuals with increased cardiometabolic disease risk, although it is unclear which measures perform best in African adults. We aimed to: 1) cross-sectionally compare the accuracy of existing waist-to-height ratio (WHtR) and waist circumference (WC) thresholds to identify individuals with hypertension, pre-diabetes, or dyslipidaemia; 2) identify optimal WC and WHtR thresholds to detect CVD risk in this African population; and 3) assess which measure best predicts 5-year CVD risk. METHODS AND RESULTS Black South Africans (577 men, 942 women, aged >30years) were recruited by random household selection from four North West Province communities. Demographic and anthropometric measures were taken. Recommended diagnostic thresholds (WC > 80 cm for women, >94 cm for men; WHtR > 0.5) were evaluated to predict blood pressure, fasting blood glucose, lipids, and glycated haemoglobin measured at baseline and 5 year follow up. Women were significantly more overweight than men at baseline (mean body mass index (BMI) women 27.3 ± 7.4 kg/m(2), men 20.9 ± 4.3 kg/m(2)); median WC women 81.9 cm (interquartile range 61-103), men 74.7 cm (63-87 cm), all P < 0.001). In women, both WC and WHtR significantly predicted all cardiometabolic risk factors after 5 years. In men, even after adjusting WC threshold based on ROC analysis, WHtR better predicted overall 5-year risk. Neither measure predicted hypertension in men. CONCLUSIONS The WHtR threshold of >0.5 appears to be more consistently supported and may provide a better predictor of future cardiometabolic risk in sub-Saharan Africa.

Point-of-use micronutrient fortification: lessons learned in implementing a preschool-based pilot trial in South Africa

This current pilot trial assessed the feasibility of implementing a point-of-use (PoU) micronutrient fortification in preschool settings. Preschool children (n = 151) aged 36–79 months were randomized into intervention (n = 76) and control (n = 75) groups, both receiving breakfast maize-porridge with added micronutrient or placebo powder for 52 school days. Process evaluation and early childhood development indicators were used to assess trial feasibility. Process evaluation results showed that the implementation components were feasible and could be delivered with high fidelity. The improvement in hemoglobin concentration in intervention and control groups were not significantly different (P = 0.250). There was medium likelihood for practical significance for the two global cognitive scores assessed: non-verbal index (intervention effects: 7.20; 95% confidence interval: 2.60, 11.81; P = 0.002, effect size: 0.55) and mental processing index (intervention effects: 2.73; 95% confidence interval: 0.25, 5.70; P = 0.072, effect size: 0.36) on the Kaufman Assessment Battery for Children, Second Edition. The lessons from this trial could help in planning/implementing future PoU micronutrient fortification trial among South African preschool children.

Stunting, adiposity, and low-grade inflammation in African adolescents from a township high school.

OBJECTIVE The objective of this study was to compare the inflammatory status of children with differences in nutritional status. METHODS This was a cross-sectional study of 184 African children aged 13-18 y from a low socioeconomic background that compared stunted with non-stunted and lean with over-fat (percentage of body fat above normal cutoff points) children. Fasting serum tumor necrosis factor-alpha, interleukin-6, C-reactive protein, and insulin were measured using high-sensitivity methods. Body composition was assessed using anthropometry and air-displacement plethysmography. T tests for parametric data and the Mann-Whitney test for non-parametric data were used to compare groups. Regression analyses and principal components analyses were done to assess relations between body composition and biochemical variables. RESULTS Of all participants 18% were stunted. Serum tumor necrosis factor-alpha of stunted girls was higher than in non-stunted girls. More of the stunted boys were over-fat compared with their non-stunted counterparts. Regression analyses showed that insulin resistance, diastolic blood pressure, and C-reactive protein contributed significantly to interleukin-6 in boys. Serum C-reactive protein, waist circumference, and body mass index clustered together in factor analysis in boys. Serum interleukin-6, waist-hip ratio, and tumor necrosis factor-alpha clustered together in factor analysis in girls. CONCLUSION An association between adiposity and stunting and between adiposity low-grade inflammation was found in this study. Interventions for stunted children focus mainly on correction of undernutrition by providing feeding schemes. Attention should, however, also be paid to changes in body composition over time to prevent excessive abdominal fat accumulation and risk for cardiovascular diseases later in life.