Body mass index across the life course: emergence of race-by-sex disparities in early childhood.

Purpose: The purpose of this study was to assess when in the life-course race-by-sex disparities in body mass index (BMI) emerge. Methods: Child Health and Development Studies participants, from whom height and weight data were collected at ages 5, 9-11, and 15-17 years, were followed up at the age of 50 years for anthropometric outcomes. Follow-up was completed for 605 subjects, 460 of whom were assessed for height and weight at the age of 50 years, had at least one available childhood BMI measure, and self-identified as either non-Hispanic black or non-Hispanic white. Linear regression analyses were conducted to determine whether interactions existed between race (black vs. white) and sex for predicting BMI at ages 5, 9-11, 15-17, and 50 years. Results: At age 5 years, BMI was independent of sex for both blacks and whites, but by the age of 9-11 years, BMI was sex-dependent in blacks, with higher BMI observed among black females. This sex dependence for BMI among blacks persisted at ages 15-17 years and age 50 years. The race-by-sex interaction was significant at ages 9-11, 15-17, and 50 years (P for interaction = 0.001, 0.002, and 0.01, respectively). Conclusions: Race-by-sex disparities in body size were observed by the age of 9-11 years and persisted until the age of 50 years. (C) 2019 Elsevier Inc. All rights reserved.