The Impact of Decaffeinated Green Tea Extract on Fat Oxidation, Body Composition and Cardio-Metabolic Health in Overweight, Recreationally Active Individuals

This study investigated the effect of decaffeinated green tea extract (dGTE), with or without antioxidant nutrients, on fat oxidation, body composition and cardio-metabolic health measures in overweight individuals engaged in regular exercise. Twenty-seven participants (20 females, 7 males; body mass: 77.5 +/- 10.5 kg; body mass index: 27.4 +/- 3.0 kg.m(2); peak oxygen uptake ((V) over dotO(2peak)): 30.2 +/- 5.8 mL.kg(-1).min(-1)) were randomly assigned, in a double-blinded manner, either: dGTE (400 mg.d(-1) (-)-epigallocatechin 3-gallate (EGCG), n = 9); a novel dGTE+ (400 mg.d(-1) EGCG, quercetin (50 mg.d(-1)) and alpha-lipoic acid (LA, 150 mg.d(-1)), n = 9); or placebo (PL, n = 9) for 8 weeks, whilst maintaining standardised, aerobic exercise. Fat oxidation ('FAT(MAX)' and steady state exercise protocols), body composition, cardio-metabolic and blood measures (serum glucose, insulin, leptin, adiponectin, glycerol, free fatty acids, total cholesterol, high [HDL-c] and low-density lipoprotein cholesterol [LDL-c], triglycerides, liver enzymes and bilirubin) were assessed at baseline, week 4 and 8. Following 8 weeks of dGTE+, maximal fat oxidation (MFO) significantly improved from 154.4 +/- 20.6 to 224.6 +/- 23.2 mg.min(-1) (p = 0.009), along with a 22.5% increase in the exercise intensity at which fat oxidation was deemed negligible (FAT(MIN); 67.6 +/- 3.6%. (V)over dotO(2peak), p = 0.003). Steady state exercise substrate utilisation also improved for dGTE+ only, with respiratory exchange ratio reducing from 0.94 +/- 0.01 at week 4, to 0.89 +/- 0.01 at week 8 (p = 0.004). This corresponded with a significant increase in the contribution of fat to energy expenditure for dGTE+ from 21.0 +/- 4.1% at week 4, to 34.6 +/- 4.7% at week 8 (p = 0.006). LDL-c was also lower (normalised fold change of 0.09 +/- 0.06) for dGTE+ by week 8 (p = 0.038). No other significant effects were found in any group. Eight weeks of dGTE+ improved MFO and substrate utilisation during exercise, and lowered LDL-c. However, body composition and cardio-metabolic markers in healthy, overweight individuals who maintained regular physical activity were largely unaffected by dGTE.

Automated summary

The study found that 8 weeks of dGTE+ improved maximal fat oxidation and exercise intensity, lowered LDL-c levels, but had minimal effects on body composition and cardio-metabolic markers in healthy, overweight individuals who maintained regular physical activity.