Drivers of adolescent adiposity: Evidence from the Australian LOOK study

To contribute to our understanding of the drivers of body composition during adolescence we sought to employ valid and reliable measures to investigate cross-sectional and longitudinal relationships between percentage body fat (%BF) and physical activity (PA), moderate and vigorous PA (MVPA), sedentary time (ST), total energy, sugar and fat intake.

Longitudinal cohort study.

We measured 556 (289 male) participants at age 12.4 (SD 0.4) years, and 269 (123 males) at 16.3 (SD 0.4) years, for %BF (dual energy X-ray absorptiometry); habitual PA, MVPA, ST (accelerometry); and dietary intake ('multi-pass' weekday and weekend 24-h recall). Accounting for likely under-reporting of energy intake (Goldberg cut-off), general linear mixed modelling was used to generate relationships with %BF.

Cross-sectional analyses indicated that 10min more MVPA per day was associated with 0.6 lower %BF (95%CI 0.4-0.9, p<0.001), and 10min less ST/day with 0.07 lower %BF (95%CI 0.00-0.15, p<0.001), independently of PA. In contrast, %BF was unrelated to total energy (p=0.4), sugar intake (p=0.2) or fat intake (p=0.9). Longitudinal analysis showed that if PA was increased by 3% (10,000 counts/day) over the 4 years, then %BF was reduced by 0.08 (95%CI 0.05-0.12, p=0.06).

The independent relationships of %BF with PA and ST, but absence of relationships with energy, sugar or fat intake, suggest that general community campaigns in a developed country directed at reducing adolescent obesity through modifications to energy intake and output would benefit from a more concerted focus on the latter.