Irisin Levels Are not Associated to Resistance Training-Induced Alterations in Body Mass Composition in Older Untrained Women with and without Obesity

Abstract

Objective: The present study aimed to determine whether Irisin levels are correlated with body composition changes following 16 weeks of resistance training (RT) in older women with and without obesity. Design, Setting, Participants, Intervention: We recruited 49 inactive women (n = 23, non-obese: < 41.0% and n = 26, obese: ≥ 41.0% of body fat) aged 61-68 years to perform 16-week of RT consisting of 10 exercises (three sets of 10 exercises, 6-12 repetitions maximum and 1-min and 30-s rest intervals between sets and exercises, respectively) with two sessions per week.

Measurements: Before and after the intervention period, blood samples were collected to determine Irisin levels and body composition (percentage body fat and fat-free mass) was measured by dual energy x-ray absorptiometry.

Results: Circulating Irisin displayed a decrease for the non-obese group as compared with pre-intervention and obese group (p = 0.01 and p = 0.04, respectively), with no change for the obese group (p = 0.79). In addition, fat mass displayed a significant reduction (p < 0.05) following the training period only for the obese group. Furthermore, there was no association between changes in circulating Irisin with body mass index, body fat, fat-free mass and muscle strength. There was an increase in muscle strength (p < 0.05), regardless of obesity status.

Conclusion: The modulation of body composition and muscle strength induced by 16-week of resistance training in older women with and without obesity is not associated with changes in circulating Irisin levels.

Keywords: Aging; myokines; obesity; resistance training.