Bidirectional Associations Between Physical Activity And Adiposity: A 7-year Longitudinal-study From Pre-puberty To Early Adulthood

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PURPOSE: This study aimed to investigate directional influences in the association between physical activity and adiposity levels in females during pubertal development. METHODS: Longitudinal associations between physical activity and adiposity levels were assessed in 396 Finnish females from pre-puberty (mean age, 11.2 years at baseline) through 1-, 2-, 4-, and 7-year follow-ups. Body weight and height were measured using an electronic scale and a stadiometer, respectively. Body fat was measured by Dual-energy X-ray absorptiometry. Body mass index (BMI) was calculated as body weight in kilograms divided by height in meters squared. Fat mass index (FMI) was calculated as total fat mass in kilograms divided by height in meters squared. Leisure-time physical activity (LTPA) level was evaluated using a WHO validated self-administrated physical activity questionnaire. Directional influences of physical activity and adiposity were examined using bivariate cross-lagged path panel model (CLPM). In this model, the auto-regressive indicates the temporal stability of the variables from one time point to the next, and cross-lagged paths assess bidirectional associations between the variables at consecutive time points (Mplus version 7.4). RESULTS: The autoregressive part of the CLPM model indicated that the temporal stability of BMI from pre-puberty to early adulthood is higher than the temporal stability of LTPA or physical inactivity over the same time period. The cross-lagged effects showed that higher BMI at baseline and at 4-year follow-up predicted lower LTPA at 1-year and 7-year follow-up, respectively (p<0.05 for both) but LTPA did not predict subsequent BMI at any time point. The model had good fit to the data (LTPA: χ2 = 44.025, p = 0.008, RMSEA = 0.046). Similar to BMI, higher FMI at baseline and at 2-year follow-up predicted lower LTPA at 2-year and 7-year follow-up, respectively (p<0.05 for both), but LTPA did not predict subsequent FMI. CONCLUSIONS: Decreased LTPA appears to be the result of fatness rather than its cause in this cohort of peripubertal girls transitioning from pre-puberty to early adulthood. Public health strategies may need to emphasize the importance of energy intake and healthier diet to keep children at healthy weight.

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