ABSTRACT
Salivary cortisol levels and saliva alpha-amylase enzymatic activity are non-invasive markers of hypothalamic-pituitary-adrenal axis and autonomic nervous system related to stress, which could be associated with excessive energy intake in response to stressors. Aim: To describe the diurnal variation of salivary cortisol levels and á-amylase activity in prepubertal girls and to assess their change after meals and physical activity episodes. Subjects and Methods: Nine normal-weight girls aged 8 to 10 years were monitored for 14 hours, from 6:00 AM to 20:00 h. Three standardized meals were administered across the day with a controlled sport competition performed at the end of the day. Saliva samples were drawn upon awakening, 30 min after awakening, before and after lunch, before and after dinner, and before-after the controlled episode of physical activity. Results: A decreasing salivary cortisol diurnal pattern was confirmed, with an initial increase occurring 30 minutes after waking up. An ascending diurnal pattern was observed for salivary amylase activity. Meals significantly increased cortisol levels, with a non-significant trend to increase amylase activity. The magnitude of physical activity during acute exercise was associated with increased salivary amylase activity (rho = 0.84; P <0.01). Cortisol levels were positively correlated with body mass index z scores (rho = 0.87; P <0.01). Conclusions: We confirmed the existence of a diurnal pattern of salivary cortisol levels and á-amylase activity in saliva that is modulated by diet and exercise. Our preliminary results also show that salivary cortisol might be related with body weight...