BMI Trajectories from Birth to Young Adulthood.

Objective: This study aimed to compare BMI trajectories from childhood to early adulthood in those with overweight and/or obesity versus severe obesity.

Methods: Longitudinal BMI values (2,542 measurements) were calculated from measured heights and weights for 103 children, adolescents, or young adults with overweight, obesity, or severe obesity. Segmented regression with splines was used to model BMI trajectories.

Results: Sixty-nine participants were classified as ever having severe obesity versus 34 who never had severe obesity. Trajectories and slopes did not differ by sex or race/ethnicity. Compared with those who never had severe obesity, BMI was higher in the group with severe obesity at all ages, and BMI slope was higher for those with severe obesity at age 14 (P = 0.002), with peak slope occurring later (18 years vs. 16 years) and higher (4.5 ± 0.5 kg/m /y vs. 2.9 ± 0.5 kg/m /y; P < 0.02). In the group without severe obesity, BMI fell below zero by the mid-20s (-0.3 ± 0.6 kg/m /y); in those with severe obesity, BMI slope never reached zero (0.9 ± 0.5 kg/m /y).

Conclusions: Youth with severe obesity, compared with their peers without, started with higher BMIs, had more rapid rates of BMI increase beginning at age 14, as well as a higher peak and longer period of increase, and never achieved weight stabilization.