Background

Research suggests that sympathoadrenal activity and fatty acid metabolism can be altered with exercise. The aim of this study was to assess the effects of an 8-month exercise program on plasma epinephrine (EPI), cortisol, and non-esterified fatty acids (NEFA) levels in non-diabetic overweight/obese individuals.

Methods

EPI, NEFA, and cortisol levels were measured during intravenous glucose tolerance testing (IVGTT) performed in 78 overweight/obese (BMI ranging between 25 and 38) non-diabetic participants (43 men and 35 women; mean age: 52±6) participating in an 8-month exercise intervention. Fasting and post-glucose bolus levels averaged over the first 20 minutes of the IVGTT were examined. Repeated measures ANOVA and Spearman rank correlation coefficients were performed to determine differences in and the association between pre- to post- intervention levels, respectively.

Results

Only post-glucose bolus cortisol levels were significantly lower after the intervention (16.0±5.8 to 14.5±5.8, p=.04). Fasting and post-bolus EPI levels were significantly associated pre- to post-intervention (Spearman’s rho=.47, p<.001 and .56, p<.001 respectively). Fasting cortisol levels and post-bolus cortisol levels were significantly associated pre- to post- intervention (Spearman’s rho=.40, p=.001 and .40, p<.001 respectively). Fasting NEFA levels were not significantly associated pre- to post- intervention (Spearman’s rho=.14, p=.25) but post-glucose bolus NEFA levels were significantly associated pre-to post intervention (Spearman’s rho=.40, p<.001).

Conclusions

Only post-bolus cortisol showed post-exercise reduction. Further analyses will examine how individual differences may relate to intervention intensity and variability in response to exercise (i.e. changes in fitness or weight). Despite their capacity to rapidly change in response to physiological demands, EPI and cortisol exhibited significant test-retest correlation over an 8-month period, both in a fasting state and in response to a glucose bolus.