To what extent have urban South African adolescents experienced the nutrition transition?

The nutrition transition is recognised as a change in dietary pattern from a low fat, high fibre diet to a high fat, high energy, low fibre diet. This change has been accompanied by an increase in nutrition related non-communicable diseases (NCDs) such as obesity, non-insulin dependant diabetes mellitus (NIDDM), and cardio-vascular disease (CVD). The impact on health is a rising concern because these NCDs are not confined to adults but are also being increasingly observed in children and adolescents in developing countries. The nutrition transition is driven by changing socio-economic conditions, food technology, distribution and marketing systems, and urbanization. The evidence on which the nutrition transition is based comes mostly from national aggregate data on adult samples and there is a dearth of information about the aetiology and characteristics of nutrition transition at a group or individual level in adolescents. The aim of this study is to investigate the dietary intake and body composition outcomes, in a sample of South African urban adolescents in the context of the nutrition transition. These adolescents have been followed from birth within the Birth to Twenty birth cohort set in Soweto and Johannesburg. A pilot study was conducted to assess the quantitative food frequency questionnaire (FFQ) which was to be administered to measure usual dietary intake. Consequently, the FFQ was modified according to the findings from the pilot study. The modified FFQ was administered to a sample of 15-year-old adolescents (n=154) and demographic factors, physical activity, pubertal development, socioeconomic status (SES) and body composition were measured using routine cohort standard protocols. Bivariate and multivariate analyses were performed to investigate the associations of these 'factors with dietary intake (total energy intake (kcal), % fat, carbohydrate, sugar and protein intake) and body composition (body mass index, relative % fat and lean mass). The macronutrient intake of the urban adolescent sample was 33.3% fat,51.8% carbohydrate, 10.7% protein and 14% added sugar as a proportion of total energy intake. The macronutrient composition of the current diet and the most commonly consumed foods suggests a transition towards the diet consumed by transitioned societies with a greater transition in the added sugar intakes. There were no significant predictors of energy intake in the linear regression analysis. No significant associations were observed between socioeconomic status (SES) and energy intake, % fat, carbohydrate or added sugar intake. However, SES was positively associated with % protein intake. Significant differences (p=O.015) in the prevalence of overweight and obesity between girls (24.7%) and boys (9.7%) were observed. The odds of being overweight or obese increased if the participant was female, had high SES and mature breast/genitalia development. None of the dietary intake variables had a significant association with the body composition outcomes. A transition towards a typical 'western 'diet is evident suggesting that this sample of adolescents have a similar dietary risk for NCDs to their counterparts in transitioned societies. Possible intervention strategies are suggested in the light of the findings from this study.