This study sought to investigate the associations between hypothalamic-pituitary-adrenal (HPA) axis functioning and HPA feedback activity to body fat distribution in a sample with a wide range of obesity values. For that purpose, 91 men and 103 women aged between 18 and 45 years with a body mass index (BMI) ranging from 19 to 35 kg/m2 were studies. The authors found an inverse association between cortisol exposure and fat mass index [FMI: fat mass/height2 (kg/m2)] in men (r=-0.55, p<0.001) and waist-to-hip ratio (WHR) in women (r=-0.49, p<0.001). FMI was strongly correlated with waist circumference (r=0.85, p<0.001) in men. These results indicated that in both men and women low cortisol exposure, which is a sign of a decreased HPA axis, was related to intra-abdominal (visceral) fat distribution. Moreover, it was observed that reduced negative feedback of the HPA axis in a nonchallenged condition was related to a higher FMI in men and a higher WHR in women. These data are in contrast with those concerning HPA axis functioning in a challenged condition with ingestion of dexamethasone (a glucocorticoid receptor agonist). More specifically, an inverse association was observed between cortisol levels after a challenged condition and waist circumference in men and WHR in women. The mechanisms to explain these opposing results between challenged and nonchallenged conditions remain speculative. Thus, these results propose that disruption of HPA axis functioning appears to be related to intra-abdominal fat accumulation.
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