Ethnic Differences in Weight Category Transition and Body Mass Index Trajectories from Adolescence to Young Adulthood in Israel

Objective: To assess ethnic differences in the transition of weight categories and in BMI trajectories from adolescence to young adulthood between Jewish and Arab populations. Methods: A retrospective cohort study, based on the centralized computerized database of ‘Clalit Health Services’, the major health service organization that insures 52% of the Israeli population. The study population consisted of 99,741 adolescents born from 1988 to 1992 who had at least one BMI measurement in the exposure (ages 17–19 years) and follow-up (age 20 to <30 years) periods. We examined differences in weight categories in young adulthood (ages 20 to <30 years), by ethnic group, and assessed whether ethnicity moderated BMI trajectories from 20 to <30 years of age. Multilevel models were applied to examine BMI trajectories. Results: A higher percentage of Arab than Jewish adolescents from the ‘underweight’, ‘normal’, and ‘overweight’ categories moved to one of the higher weight categories in young adulthood (p < 0.001 for all). In the ‘underweight’, ‘normal’, ‘overweight’, and ‘obese’ weight categories, the increase in BMI with increasing age was lower for Jews (p < 0.001 for all). Conclusions: Many adolescents, even if not obese, have increasing BMI trajectories at ages 17–19 and move to a higher weight category in adulthood. Arab adolescents constitute a risk group for rapid BMI increase as they transition to adulthood. The present study could contribute to a better understanding of BMI dynamics and, in turn, to the development of more effective public health and policy interventions.