Leptin Predicts a Decline in Moderate to Vigorous Physical Activity in Minority Female Children at Risk for Obesity

Background Leptin may influence moderate to vigorous physical activity (MVPA) at the start of puberty. The direction and magnitude of this association are unclear.

Objectives To determine the effect of baseline leptin on MVPA over 1 year in minority girls at high risk for obesity.

Methods Data came from TRANSITIONS, a longitudinal observational study on the age-related MVPA decline. Fifty peripubertal girls aged 8-11 years at baseline participated. Baseline leptin (ng·mL^-1) was collected via a duplicated assay using a double antibody radio immune assay. MVPA (min·d^-1) was measured using accelerometers for at least four 10-h days on a quarterly basis for up to 1 year.

Results Continuous leptin was negatively related to MVPA (P = 0.001) independent of central adiposity at baseline and predicted the MVPA decline over 1 year (P = 0.002). For descriptive purposes, baseline leptin was dichotomized at the sample median into ‘high leptin’ and ‘low leptin’ categories to determine whether MVPA trajectories differed between these groups. Girls with ‘low leptin’ at baseline had significantly higher levels of MPVA at baseline, visit 1 and visit 2 compared to girls with ‘high leptin’.

Conclusions High leptin levels predicted nearly a 12.6% decline in MVPA over 1 year. These findings provide support for the biological basis of declining MVPA as girls enter puberty.