Physical activity attenuates the effect of low birth weight on insulin resistance in adolescents: findings from two observational studies

Abstract

Objective: To examine whether physical activity influences the association between birth weight and insulin resistance in adolescents.

Research design and methods: The study comprised adolescents who participated in two cross-sectional studies: the Healthy Lifestyle in Europe by Nutrition in Adolescence (HELENA) study (n = 520, mean age = 14.6 years) and the Swedish part of the European Youth Heart Study (EYHS) (n = 269, mean age = 15.6 years). Participants had valid data on birth weight (parental recall), BMI, sexual maturation, maternal education, breastfeeding, physical activity (accelerometry, counts/minute), fasting glucose, and insulin. Insulin resistance was assessed by homeostasis model assessment-insulin resistance (HOMA-IR). Maternal education level and breastfeeding duration were reported by the mothers.

Results: There was a significant interaction of physical activity in the association between birth weight and HOMA-IR (logarithmically transformed) in both the HELENA study and the EYHS (P = 0.05 and P = 0.03, respectively), after adjusting for sex, age, sexual maturation, BMI, maternal education level, and breastfeeding duration. Stratified analyses by physical activity levels (below/above median) showed a borderline inverse association between birth weight and HOMA-IR in the low-active group (standardized β = -0.094, P = 0.09, and standardized β = -0.156, P = 0.06, for HELENA and EYHS, respectively), whereas no evidence of association was found in the high-active group (standardized β = -0.031, P = 0.62, and standardized β = 0.053, P = 0.55, for HELENA and EYHS, respectively).

Conclusions: Higher levels of physical activity may attenuate the adverse effects of low birth weight on insulin sensitivity in adolescents. More observational data, from larger and more powerful studies, are required to test these findings.

FIG. 1.

Graphical representation of the standardized regression slopes (birth weight – Ln HOMA-IR) by levels of physical activity in adolescents from the HELENA study and the EYHS. High/low physical activity was defined as being above/below the age-, sex-, and study-specific median values for average physical activity (counts/minute). The regression models were adjusted for sex, age, sexual maturation, BMI, maternal education, and breastfeeding. The standardized coefficients are interpreted as the number of SDs that the outcome changes as a result of 1-SD change in the predictor. PA, physical activity.

FIG. 2.

Adjusted means (and SEs) for Ln HOMA-IR according to birth weight groups and levels of physical activity in adolescents from the HELENA study and the EYHS. High/low physical activity was defined as being above/below the age-, sex-, and study-specific median values for average physical activity (counts/minute). The ANCOVA models were adjusted for sex, age, sexual maturation, BMI, maternal education, and breastfeeding. Fitted lines for the means given are also represented. PA, physical activity; T, tertile.