Soyang Kwon, Kathleen F. Janz, Elena M. Letuchy, Trudy L. Burns, Steven M. Levy

To identify distinct body mass index (BMI) percentile trajectories during early childhood and examine adiposity levels in childhood and early adulthood according to the BMI percentile trajectories. Iowa Fluoride Study cohort parents (n = 1,093) reported their child's anthropometric data on average six times between ages 0 and 23 months. A subset of the cohort underwent DXA scans at approximately age 8 years (n = 495) and again at approximately age 19 years (n = 314). Group-based trajectory analysis was conducted to identify distinct BMI percentile trajectories from ages 0 to 23 months. Sex-specific age-adjusted linear regression analyses were conducted to compare fat mass index in childhood and early adulthood among subgroups that follow the distinct BMI percentile patterns. Four BMI percentile patterns were identified: consistently low (group 1: 9.8%), increase in the second year (group 2: 33.7%), increase in the first year (group 3: 23.9%), and consistently high (group 4: 32.6%). Compared with group 2 females, groups 3 and 4 females had higher fat mass index in childhood and early adulthood (P < 0.05). However, no significant difference was found in males. Females who experience a steep increase of BMI percentile in the first year of life, as opposed to a steep increase in the second year of life, may have higher body fat later in life, but this was not found in males.