ObjectivesGuatemala has experienced rapid increases in adult obesity. We characterized body composition trajectories from adolescence to mid‐adulthood and determined the predictive role of parental characteristics, early life factors, and a nutrition intervention.MethodsOne thousand three hundred and sixty‐four individuals who participated as children in a nutrition trial (1969–1977) were followed prospectively. Body composition characterized as body mass index (BMI), fat mass index (FMI), and fat‐free mass indices (FFMI), was available at four ages between 10 and 55 years. We applied latent class growth analysis to derive sex‐specific body composition trajectories. We estimated associations between parental (age, height, schooling) and self‐characteristics (birth order, socioeconomic status, schooling, and exposure to a nutrition supplement) with body composition trajectories.ResultsIn women, we identified two latent classes of FMI (low: 79.6%; high: 20.4%) and BMI (low: 73.0%; high: 27.0%), and three of FFMI (low: 20.2%; middle: 55.9%; high: 23.9%). In men, we identified two latent classes of FMI (low: 79.6%; high: 20.4%) and FFMI (low: 62.4%; high: 37.6%), and three of BMI (low: 43.1%; middle: 46.9%; high: 10.0%). Among women, self's schooling attainment inversely predicted FMI (OR [being in a high latent class]: 0.91, 95% CI: 0.85, 0.97), and maternal schooling positively predicted FFMI (OR: 1.16, 95% CI: 0.97, 1.39). Among men, maternal schooling, paternal age, and self's schooling attainment positively predicted FMI. Maternal schooling positively predicted FFMI, whereas maternal age and paternal schooling were inverse predictors. The nutrition intervention did not predict body composition class membership.ConclusionsParents' age and schooling, and self's schooling attainment are small but significant predictors of adult body composition trajectories.