A 4-Yr Mixed Longitudinal Study of Health Behaviors and Fat Mass Accrual during Adolescence and Early Adulthood
Bibliographic record
Abstract
PURPOSE: Physical activity (PA), sedentary time (SED), and energy intake (EI) are associated with fat mass accrual in children and youth. Previous studies relied primarily on cross-sectional designs and proxy measures of body composition such as body mass index. We aimed to prospectively investigate associations between PA, SED, EI, and total body fat mass accrual using dual-energy x-ray absorptiometry. METHODS: This analysis of the mixed longitudinal Healthy Bones III Study included data from 312 participants (138 boys age 9 to 21 yr at baseline). For each participant, we acquired a maximum of four annual total body dual-energy x-ray absorptiometry scans from which we determined fat mass (in kilograms; n = 748 observations). We assessed total PA, moderate-to-vigorous PA (MVPA) and SED with accelerometers (ActiGraph GT1M) and measured EI via 24-h dietary recall. We fit sex-specific multilevel models adjusting for maturity (years from age at peak height velocity (APHV)), weight status, ethnicity, total PA, MVPA, SED, and EI. RESULTS: Boys and girls demonstrated divergent trajectories of fat mass accrual; rate of fat mass accrual in girls was four times greater than boys at APHV and increased across adolescence, whereas boys' fat mass plateaued after APHV. In boys, within-person change in MVPA negatively predicted fat mass independent of SED; each annual increase in MVPA of 6 min·d -1 was associated with a 0.21-kg lower fat mass. In girls, between-person average MVPA negatively predicted fat mass accrual independent of SED; greater MVPA of 4 min·d -1 across adolescence was associated with a 0.31-kg lower fat mass. CONCLUSIONS: MVPA demonstrates an independent and negative effect on fat mass in boys and girls. Given different trajectories of fat mass accrual and movement behaviors between boys and girls, PA interventions aimed at preventing obesity in youth may benefit from a sex and gendered approach.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.001 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.001 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.001 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".