Body-fat distribution and responsiveness of the pituitary-adrenal axis to corticotropin-releasing-hormone stimulation in sedentary and exercising women

Excess upper-body (android) fat is considered an health hazard. Exercise tr aining is known to have the potential to modify body composition and to ind uce a preferential loss of abdominal fat. We studied and compared the compo sition of whole body and major body regions using dual-energy X-ray absorpt iometry (DEXA) in 21 exercising (3-4 hours of intense physical activity/day ) and 21 sedentary eumenorrhoic women of similar ages, body mass index (BMI ), waist-to-hip ratio (WHR) and age of menarche. In a small number of women in each group (6 out of 21), the ACTH and cortisol response to CRH test an d the 24-h urinary cortisol excretion was evaluated. Exercising women had 1 0% higher total and leg lean mass (p<0.05), and 38% lower total fat mass (p <0.01) than sedentary women. Furthermore, the proportion of android fat was 22% lower in exercising than sedentary women (p<0.01), while the proportio n of lower-body (gynoid fat) was unchanged. BMI and WHR were not different between the two groups, while the android/gynoid fat ratios were 16% lower in exercising than in sedentary women (p<0.01). In the exercising women, AC TH and cortisol plasma levels, as well as the 24-h urinary cortisol excreti on, were significantly (p<0.01) higher than in the sedentary women studied. In these subjects, a direct relationship between the peak Delta percentage increases of ACTH and cortisol after the CRH test and the proportion of an droid fat was found (r=0.60, p<0.05 acid r=0.69, p<0.02, respectively). The se results demonstrate that in women who practise intense exercise there ar e significant differences in body fat distribution in comparison to sedenta ry women, with a marked less amount of android fat, and suggest that this d ifference may be related to a reduced response of the pituitary-adrenal axi s to CRH. (C) 1999, Editrice Kurtis.