Abstract
BackgroundThe cardio-metabolic and antioxidant health benefits of caffeinated green tea (GT) relate to its catechin polyphenol content. Less is known about decaffeinated extracts, particularly in combination with exercise. The aim of this study was therefore to determine whether a decaffeinated green tea extract (dGTE) positively influenced fat oxidation, body composition and exercise performance in recreationally active participants.MethodsFourteen, recreationally active males participated in a double-blind, placebo-controlled, parallel design intervention (mean ± SE; age = 21.4 ± 0.3 yrs; weight = 76.37 ± 1.73 kg; body fat = 16.84 ± 0.97%, peak oxygen consumption [nttttttt dot{mathrm{V}}{mathrm{O}}_{2mathrm{peak}} ntttttt] = 3.00 ± 0.10 L·min−1). Participants were randomly assigned capsulated dGTE (571 mg·d−1; n = 7) or placebo (PL; n = 7) for 4 weeks. Following body composition and resting cardiovascular measures, participants cycled for 1 hour at 50% nttttttt dot{mathrm{V}}{mathrm{O}}_{2mathrm{peak}} ntttttt, followed by a 40 minute performance trial at week 0, 2 and 4. Fat and carbohydrate oxidation was assessed via indirect calorimetry. Pre-post exercise blood samples were collected for determination of total fatty acids (TFA). Distance covered (km) and average power output (W) were assessed as exercise performance criteria.ResultsTotal fat oxidation rates increased by 24.9% from 0.241 ± 0.025 to 0.301 ± 0.009 g·min−1 with dGTE (P = 0.05; ηp2 = 0.45) by week 4, whereas substrate utilisation was unaltered with PL. Body fat significantly decreased with dGTE by 1.63 ± 0.16% in contrast to PL over the intervention period (P < 0.001; ηp2 = 0.84). No significant changes for FFA or blood pressure between groups were observed. dGTE resulted in a 10.9% improvement in performance distance covered from 20.23 ± 0.54 km to 22.43 ± 0.40 km by week 4 (P < 0.001; ηp2 = 0.85).ConclusionsA 4 week dGTE intervention favourably enhanced substrate utilisation and subsequent performance indices, but did not alter TFA concentrations in comparison to PL. The results support the use of catechin polyphenols from dGTE in combination with exercise training in recreationally active volunteers.
Highlights
The health benefits of polyphenols found in green tea (GT), the unfermented leaves of the tea plant, Camellia sinensis, have been extensively investigated in the last fifteen years [1,2,3,4,5,6,7]
Baseline characteristics and resting measures Intervention groups were matched for age, height, weight, body fat and V_O2peak at baseline (Table 1)
Net bodyweight reduction was similar between groups across the intervention (0.64 ± 0.17 kg for PL; F = 12.33, P = 0.001; ηp2 = 0.67), and 0.60 ± 0.21 kg for decaffeinated green tea extract (dGTE); F = 6.27, P = 0.014; ηp2 = 0.51 within group)
Summary
The health benefits of polyphenols found in green tea (GT), the unfermented leaves of the tea plant, Camellia sinensis, have been extensively investigated in the last fifteen years [1,2,3,4,5,6,7]. GT strategies (including reduced circulating cholesterol and triglyerides [10], increased thermogenesis and whole body fat oxidation [1,3,11], reduced blood pressure [7,12,13] and improved body mass index ratios [5,14,15,16,17]) These health benefits, in part, relate to the bioactive catechin polyphenol content of GT, of which (−)-epigallocatechin-3-gallate (EGCG) can account for between 50–80% of the total catechin content [18]. GT catechins may influence specific signalling molecules, including PGC1α, leading to gene expression of fat metabolism enzymes [20] Whilst such mechanisms are currently under debate, strategies to enhance fat oxidation, body composition and cardiovascular efficiency in conjunction with physical activity are of pertinence to the general population. The aim of this study was to determine whether a decaffeinated green tea extract (dGTE) positively influenced fat oxidation, body composition and exercise performance in recreationally active participants
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