Effects of Aerobic Exercise on the Serum Leptin Level and Heart Rate Variability in the Obese Girl Children

Objective. The present study examined the effects of a 16-week aerobic exercise (AE) on the serum leptin level and heart rate variability (time domain and frequency domain) in the obese girl children and correlation coefficients of changes between the serum leptin level and heart rate variability after a 16-week AE intervention. Methods. 36 participants were randomly assigned to either aerobic exercise (AE, n = 18) or obese group (n = 18). The obese girl children in the AE group conducted a 16-week (4 times per week and 60 min per time) exercise protocols, and the obese group did not perform regular physical training during 16 weeks of study. Then, the serum leptin level and HRV (time domain and frequency domain) were measured in all subjects before and after AE intervention. Results. (1) After 16-week AE intervention, compared with pre-exercise, LF/HF decreased $\left(P<0.05\right)$ , HF, SDNN, and RMSSD significantly increased ( $P<0.05$ and $P<0.01$ ), and there was no significant difference in LF $\left(P>0.05\right)$ in the AE group. Nevertheless, there was no significant change before and after the test in the serum leptin level and HRV of the obese group ( $P>0.05$ , respectively). (2) After 16-week AE intervention, compared with the obese group, SDNN and HF significantly increased ( $P<0.05$ , respectively), LF/HF significantly decreased $\left(P<0.05\right)$ in the AE group, but there was no significant difference in RMSSD and LF between the obese group and AE group. (3) The reduction variables of the serum leptin level before and after the AE intervention are positively correlated with the reduction in the LF/HF (r = 0.478, $P<0.05$ ) and negatively correlated with the increasing in the RMSSD (r = −0.482, $P<0.05$ ). But there is no significant association between the reduction in the serum leptin level and the change of LF, HF, and SDNN ( $P>0.05$ , respectively). Conclusion. 16-week AE significantly reduced the serum leptin level and improved cardiac autonomic function in the obese girl children. Moreover, the reduction in the serum leptin level was associated with the increase in parasympathetic activation and improved sympathetic-vagus balance after AE intervention. More research is needed to see whether the effect of exercise on leptin levels in obese girl children can reduce the risk of cardiovascular disease in adulthood.