The Effect of Green Tea Extract on Fat Oxidation at Rest and during Exercise: Evidence of Efficacy and Proposed Mechanisms

Abstract

Green tea is made from the leaves of the Camellia sinensis L plant, which is rich in polyphenol catechins and caffeine. There is increasing interest in the potential role of green tea extract (GTE) in fat metabolism and its influence on health and exercise performance. A number of studies have observed positive effects of GTE on fat metabolism at rest and during exercise, following both shorter and longer term intake. However, overall, the literature is inconclusive. The fact that not all studies observed effects may be related to differences in study designs, GTE bioavailability, and variation of the measurement (fat oxidation). In addition, the precise mechanisms of GTE in the human body that increase fat oxidation are unclear. The often-cited in vitro catechol-O-methyltransferase mechanism is used to explain the changes in substrate metabolism with little in vivo evidence to support it. Also, changes in expression of fat metabolism genes with longer term GTE intake have been implicated at rest and with exercise training, including the upregulation of fat metabolism enzyme gene expression in the skeletal muscle and downregulation of adipogenic genes in the liver. The exact molecular signaling that activates changes to fat metabolism gene expression is unclear but may be driven by PPAR-γ coactivator 1-α and PPARs. However, to date, evidence from human studies to support these adaptations is lacking. Clearly, more studies have to be performed to elucidate the effects of GTE on fat metabolism as well as improve our understanding of the underlying mechanisms.

Influence of green tea catechins on oxidative stress metabolites at rest and during exercise in healthy humans

“…GTC effects on exercise capacity or under resting conditions, and the oxidative stress defense system when consumed over short or long periods remained an interesting topic over the recent years [4,[26][27][28]. To our knowledge, this is the first time to compare the effect of single dose of GTC supplementation on the oxidative stress biomarkers of fat oxidation metabolites at resting as well as during exercise conditions.…”

“…A C C E P T E D ACCEPTED MANUSCRIPT 4 However, few studies are available concerning the effects of GTC (decaffeinated) on exercise induced oxidative stress blood biomarkers. Venables et al reported that acute consumption of decaffeinated green tea extract (890±13 mg polyphenol: 366±5 mg EGCG) in the 24 h period significantly (P<0.01) increased fat oxidation in subjects during a single moderate exercise bout at 60% of maximal oxygen uptake (60% VO 2 max), wherein average fat oxidation rate were 17 % higher whilst improving insulin sensitivity and glucose tolerance in healthy young men [17].…”

“…Whilst, at resting condition the fat is the predominant fuel for energy demand in human. Number of researches have been focused on the strategies and interventions to enhance rates of fat metabolism at rest as well as during exercise [1][2][3][4][5].…”

Green tea extract supplementation does not hamper endurance-training adaptation but improves antioxidant capacity in sedentary men

“…Emerging evidence indicates that green tea extracts (GTE) contain important polyphenol compounds (i.e., catechins) that underlie antioxidant mechanisms (Ruch et al 1989;Yang et al 2001;Higdon and Frei 2003), which could attenuate oxidative stress and enhance substrate metabolism. The catechins have been classified based on the number of hydroxyl groups within their chemical structures, including epicatechin (EC), gallocatechin, epigallocatechin (EGC), catechin gallate, gallocatechin gallate, epicatechin gallate (ECG), and epigallocatechin gallate (EGCG) (Higdon and Frei 2003;Hodgson et al 2013). Although many studies report positive effects of GTE on attenuating oxidative stress (Murase et al 2008;Panza et al 2008;Haramizu et al 2011) and improving endurance capacity (Murase et al , 2006Richards et al 2010), not all studies agree (Eichenberger et al 2009(Eichenberger et al , 2010.…”

The Effect of short-term aerobic exercise and green tea consumption on MFO, ‎Fatmax, body composition and lipid profile in sedentary postmenopausal ‎‎women

“…Totally, there is a high correlation between lipoprotein lipase activity and blood triglyceride levels (removal of TG from the blood); hence, the decline of TG following aerobic exercise is justified in our study [24]. The changes in the expression of fat metabolism genes could be brought about with chronic exercise training; the expression of fat metabolism genes could include the upregulation of fat metabolism enzyme gene in skeletal muscle and down regulation of hepatic adipogenic gene expression [35]. Plus, green tea has cholesterol-lowering property.…”