The Effect of Green Tea Extract on Fat Oxidation during 1hour Arm Cycle Exercise

Abstract

PURPOSE: Decaffeinated Green Tea Extract (GTE) supplementation can increase fat oxidation during leg exercise, but many people cannot perform leg exercise. The purpose of this study was to investigate the effect of GTE supplementation on fat utilization during 1h arm cycle exercise. We hypothesized that GTE supplementation will increase lipolysis and fat oxidation. METHODS: This was a randomized, controlled, triple blind study with a crossover design. 8 healthy adults (4 females, 23-37yrs) performed an incremental arm cycle test to exhaustion followed by 4 time trials at fixed workloads. After an 8h fast subjects did 1h of arm cycling at 50% Wpeak. Subjects were randomly assigned to either decaffeinated GTE (650mg, 611mg EGCG) or placebo (PLA) for 4wks. Subjects then repeated the 1hr arm cycle trial. A 4wk washout period was followed by the corresponding crossover trial. 5ml of blood were drawn pre and post exercise while respiratory gases were collected continuously. Plasma glycerol and free fatty acid (FFA) concentrations were assessed with commercially available analysis kits. The study was powered at 1-β > 95%, with α = 0.05 given a reported effect size of F = 3.39 for the time by treatment interaction. RESULTS: Mean VO2 during all 1hr trials showed no significant differences (.83-.89 ± .19-.25 L/min, p = .460). Similarly, mean total energy expenditure (EE) showed no differences across all trials (264.58 - 266.15 kcal, p = .420). The percentage of total EE from fat oxidation was higher after GTE supplementation compared to PLA, but this difference was not significant (22.83 ± 11.57 to 25.38 ± 11.3 % vs. 23.39 ± 9.97 to 20.69 ± 8.9%, p = .532). There were no significant changes in g/min of fat oxidized between treatments before and after supplementation (GTE = .11 ± .08 to .12 ± .06 vs. PLA = .10 ± .05 to .09 ± .04, p = .220. Blood Glycerol concentration increased post exercise in all trails, with no significant differences between treatments (8.55 ± 3.44 mg/dl to 8.47 ± 2.6 vs. 10.05 ± 2.86 to 8.99 ± 3.51 mg/dl, p = .527). FFA concentration was also increased post exercise for both groups with no significant difference between treatments (8.30 ± 3.8 mg/dl to 8.69 ± 2.59 vs. 9.06 ± 4.49 to 7.16 ± 3.79, p = .234). CONCLUSION: These results suggest that there is no effect of 1m GTE supplementation on fat utilization during 1hr arm cycle exercise at 50% Wpeak.