Dietary content and combined training, but not daily physical activity, are associated with 6-month bone mineral changes in adolescents with obesity: a secondary analysis of the PAC-MAnO trial

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Purpose: The present study aimed to explore the influence of diet and physical activity (PA) changes on bone mineral content (BMC) and density (BMD) alterations in adolescents with obesity undergoing a weight loss program. Methods: Six-month longitudinal data from 71 adolescents (aged 15.1 [± 1.6] years; 57.7% girls) with a BMI z-score of 3.03 (± 0.78), previously recruited for the PAC-MAnO trial, were analyzed using Generalized Estimation Equations for over time changes and linear regressions with BMC, BMD and BMD z-score as dependent variables, adjusting for confounders (including type of exercise- aerobic vs. combined). Results: Adjusting for confounders, changes in carbohydrate (CH) and protein content showed to positively and negatively predict BMD z-score variance, respectively (β = 0.44, 95%CI: 0.01, 0.04, p < .001); β = -0.57, 95%CI: -0.06, -0.03, p < .001), yet no associations were found between PA and bone-related parameters. Combined exercise showed better results on BMC compared to aerobic exercise (β = 0.09, 95%CI: 0.05 to 0.13, p < .001). Conclusions: Increased CH content, instead of protein, may be associated with BMD improvements in adolescents with obesity. Type of exercise may moderate the impact of PA on bone health. Trial registration: Clinicaltrials.gov NCT02941770. What is Known • Adolescents with obesity may be at a higher risk of osteopenia/osteoporosis • Obesity and inadequate diet and physical activity (PA) may have an adverse effect on bone metabolism What is New • Improvements in adiposity and muscle mass and increased diet carbohydrate content are associated with bone mineral density (BMD) improvements • Type of exercise (i.e., combined training vs. aerobic) may moderate the impact of PA on BMD, and calcium intake may mediate this impact.

AVS was supported by the Portuguese Foundation for Science and Technology (SFRH/BD/130193/2017). Open access funding provided by FCT|FCCN (b-on). AVS was supported by the Portuguese Foundation for Science and Technology (SFRH/BD/130193/2017).

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