Fat Metabolism During Acute Resistance Exercise in Lean and Obese Sedentary Men

Abstract

PURPOSE: To identify in sedentary lean (LN) and obese (OB) men the effect of acute resistance exercise (RE) on: 1) subcutaneous abdominal adipose tissue (SCAAT) lipolysis and 2) whole-body substrate oxidation. METHODS: Lipolysis was monitored in 5 LN ( age, 25.8 ± 3.1 years; body fat, 13.8 ± 1.8%) and 5 OB (age, 28.6 ± 2.6 years; body fat, 34.9 ± 1.9%) men before, during, and for 24 hours after one high-intensity RE session (3 sets, ~85% 10RM). Blood was taken every 20 min (hours 1-3) and energy expenditure (EE) was measured before and immediately after RE for 40 min. One microdialysis probe (Elite 20 kDa, CMA/ Microdialysis) was inserted into the SCAAT and was perfused with saline containing 10 mM ethanol. Dialysate was collected every 20 min (hours 1-3) or every hour (hours 4-24) and analyzed for ethanol and glycerol (G). Two hours after RE, a liquid meal (25% of daily EE) was given and thereafter, participants were free to go through their normal daily activities while consuming the assigned liquid meals. RESULTS: Dialysate G concentration (an index of lipolysis) increased during RE compared to baseline (BL) in both LN (mean ± SEM: BL, 44.3 ± 8.1; RE, 98.5 ± 20.2 μmol/L; p=0.05) and OB (BL, 49.6 ± 11.3; RE, 79.8 ± 12.7 μmol/L; p=0.01). G concentrations remained elevated immediately post-RE vs. BL in the LN only (BL, 44.3 ± 8.1; post-RE, 74.2 ± 10.3 μmol/L; p=0.02). For the remainder of the day G concentration was only different from baseline at hour 13 of 24 in the LN (BL, 44.3 ± 8.1; hour 13, 27.5 ± 3.5 μmol/L; p=0.03). Plasma insulin concentrations were at least 2-fold higher in the OB vs. LN at all time points (LN, 8.8 ± 1.5; OB, 32.6 ± 9.9 uU/mL; p=0.04). EE was elevated immediately post-RE compared to pre-RE in LN (pre-RE, 70.3 ± 3.8; post-RE, 85.3 ± 6.6 kcal/hr; p=0.03) and OB (pre-RE, 96.2 ± 2.8; post-RE, 122.0 ± 3.7; p=0.02). Fat oxidation (FOX) was higher post-RE compared to pre-RE in the LN (pre-RE, 4.1 ± 0.7; post-RE, 6.2 ± 0.6 g/hr, p=0.01) and OB (pre-RE, 4.8 ± 0.4; post-RE, 8.4 ± 0.6, p=0.03). CONCLUSIONS: The mechanism behind RE contributing to improved body composition may in part be due to enhanced SCAAT lipolysis and improved whole body EE and FOX in response to RE in LN and OB men. (MDC supported by EAS)