Open AccessFat‐free mass mediates the association between birth weight and aerobic fitness in youth
Author(s) -
RIDGWAY C. L.,
BRAGE S.,
ANDERSSEN S.,
SARDINHA L. B.,
ANDERSEN L. B.,
EKELUND U.
Publication year - 2011
Publication title -
international journal of pediatric obesity
Language(s) - English
Resource type - Journals
eISSN - 1747-7174
pISSN - 1747-7166
DOI - 10.3109/17477166.2010.526225
Subject(s) - aerobic exercise , medicine , birth weight , demography , body mass index , physical fitness , population , vo2 max , cardiorespiratory fitness , zoology , physical therapy , heart rate , pregnancy , biology , blood pressure , environmental health , sociology , genetics
Objective . To investigate whether birth weight acts as a biological determinant of later aerobic fitness, and whether fat‐free mass may mediate this association. Methods . The European Youth Heart Study (EYHS) is a population‐based cohort of two age groups (9 and 15 years) from Denmark, Portugal, Estonia and Norway. Children with parentally reported birth weight >1.5 kg were included (n = 2 749). Data were collected on weight, height, and skinfold measures to estimate fat mass and fat‐free mass. Aerobic fitness (peak power, watts) was assessed using a maximal, progressive cycle ergometer test. Physical activity was collected in a subset (n = 1 505) using a hip‐worn accelerometer and defined as total activity counts/wear time, all children with >600 minutes/day for ≥3 days of wear were included. Results . Lower birth weight was associated with lower aerobic fitness, after adjusting for sex, age group, country, sexual maturity and socio‐economic status (ß = 5.4; 95% CI: 3.5, 7.3 W per 1 kg increase in birth weight, p < 0.001). When fat‐free mass was introduced as a covariate in the model, the association between birth weight and aerobic fitness was almost completely attenuated (p = 0.7). Birth weight was also significantly associated with fat‐free mass (ß = 1.4; 95% CI: 1.1, 1.8, p < 0.001) and fat‐free mass was significantly associated with aerobic fitness (ß = 3.6; 95% CI: 3.4, 3.7, p < 0.001). Further adjustment for physical activity did not alter the findings. Conclusion . Birth weight may have long‐term influences on fat‐free mass and differences in fat‐free mass mediate the observed association between birth weight and aerobic fitness.