Magnitude, trends, transitions, and drivers of the double burden of malnutrition among adolescent girls in urban slums, Kenya: findings from a longitudinal study (2017–2019)

Background: The double burden of malnutrition (DBM) in adolescence has adverse short- and long-term, intergenerational health, developmental, and economic consequences. This study aimed to investigate the magnitude, trends, transitions, and drivers of population-level DBM (stunting, thinness, and overweight/obesity) among adolescent girls in urban slums in Nairobi, Kenya. Methods: Adolescent girls (n = 419) were recruited from two slums and followed up from 2017 to 2019. Socio-demographic and anthropometric data were collected. BMI-for-age (BFAZ) and height-for-age (HFAZ) Z-scores were computed and categorised as thinness (BFAZ < -2.0 SD), overweight/obesity (BFAZ > 1.0 SD), stunting (HFAZ < -2.0 SD) and normal otherwise. Mixed effects logistic regression and continuous-time multi-state models were used to assess the factors associated with, and the transitions across the nutrition indicators respectively, over the three years. Results: At recruitment (2017), prevalence of overweight/obesity (12.2%) was slightly higher than thinness (8.6%) and stunting (8.8). Between 2017 and 2019, there was a 5% point and 2% point increase in overweight/obesity and stunting respectively, and a 4% decline in thinness. A higher proportion of transition from normal nutritional status to overweight/obese (7%), compared to thin (2%) and stunted (4%) was observed. Family size (RRR = 0.75; 95% CI = 0.57–0.99) was inversely associated with overweight/obesity. Luo ethnicity (HR = 3.25; 95% CI = 1.12–9.44), Viwandani slum (HR = 2.68; 95% CI = 1.08–6.63), and depression score (HR = 1.33; 95% CI = 1.01–1.75) were positively associated with a transition from normal status to overweight/obesity. Adverse childhood experiences (ACEs) (OR = 1.24; 95% CI = 1.05–1.46), and family size (OR = 1.39; 95% CI = 1.08–1.81) were positively associated with stunting. Public school attendance (HR = 2.89; 95% CI = 1.05–7.94) was positively associated with transition to stunting. Conclusion: The prevalence of overweight/obesity, as well as transitions to overweight/obesity were higher compared to undernutrition (stunting and thinness). Double-duty and multi-sectoral interventions that consider demographic (family, ethnicity), environmental (neighbourhood, school), and psychosocial (ACE, depression score) factors that may drive DBM in adolescent girls living in urban slums are recommended, to address DBM and reverse the growing trend in overweight/obesity. Integration of social protection, mental health, and nutrition interventions is important to address DBM in urban slums and similar contexts.