Dietary Practices and Adolescent Obesity in Secondary School Learners at Disadvantaged Schools in South Africa: Urban–Rural and Gender Differences

South Africa has a high prevalence of obesity in black female adolescents and a paucity of knowledge regarding contributing dietary practices. The aim of this study was to assess the dietary practices and weight status of male and female adolescents at secondary schools in the Eastern Cape province in urban and rural areas. Sixteen schools and grade 8–12 learners (N = 1360) were randomly selected from three health districts comprising poor disadvantaged communities. A short unquantified food frequency questionnaire was used to collect data on learners’ usual eating practices with regards to weekly meal pattern, breakfast consumption, foods taken to school, takeaways, and snacks eaten while watching television (TV). Body mass index measurements were determined for each learner. Prevalence of combined overweight and obesity differed significantly between genders, 9.9% in males versus 36.1% in females (p < 0.001). Significant gender differences were noted regarding eating practices. Females had a higher frequency of eating sugary snacks (p < 0.001) and a lower frequency of eating breakfast (p < 0.01) than males. Females ate significantly more fried fish (p < 0.05), pizza (p < 0.05) fat cakes (fried dough balls) (p < 0.05), hotdogs (p < 0.01), candy (p < 0.001), cake (p < 0.01), and crisps (p < 0.001). Compared to urban areas, the frequency of eating breakfast (p < 0.01) and sugary snacks (p < 0.05) was significantly higher in rural areas. Significantly more learners in urban areas consumed boerewors (beef sausage) rolls (p = 0.027), hamburgers (p = 0.004), and soft drinks (p = 0.019), while more learners in the rural areas consumed cordial (p = 0.001). In conclusion, a high prevalence of combined overweight and obesity was found in black female adolescents and a high prevalence of poor dietary practices was observed, with significant gender and urban–rural differences.