Cortisol reactivity, delay discounting and percent body fat in Chinese urban young adolescents.

The purpose of this study is to test the relation of cortisol reactivity, delay discounting and percent body fat (PBF) in adolescents aged 12-13 years (N=87), and evaluate the delay discounting as potential components in models of adolescent obesity. Anthropometry and body composition measurements were assessed in adolescents. The cortisol reactivity to Trier Social Stress Test for Children (TSST-C) and delay discounting were measured. The result showed increased cortisol reactivity and greater delay discounting were associated with higher PBF in girls. Structural equation modeling supported greater delay discounting as a mediator of relations between increased cortisol reactivity and PBF in adolescent girls. The proposed mediation model indicated that cortisol reactivity is linked to PBF through delay discounting, thereby supporting a significant indirect relationship. The direct relationship between increased cortisol reactivity and higher PBF was significant in a model that did not include delay discounting, and was still significant in the mediation model that included delay discounting. This study provides the first evidence that greater delay discounting may partially account for the relationship of hyperactivity of the HPA-axis and higher PBF in girls.