Effect of short-term epigallocatechin-3-gallate supplementation on the thermic effect of feeding and resting metabolic rate

Abstract

The sympathetic nervous system (SNS) both provides tonic support of resting metabolic rate (RMR) and mediates approximately one-third of the thermic effect of feeding (TEF), the latter accounting for ~10% of daily energy expenditure. Epigallocatechin-3-gallate (EGCG), the most abundant and bioactive catechin in green tea, inhibits the catecholamine-degrading action of the enzyme catechol-O-methyltransferase, thereby prolonging SNS activation. Accordingly, we hypothesized that short-term EGCG supplementation would augment RMR and TEF in healthy adult humans. METHODS: Sixteen subjects reported to our lab on two mornings (≥ 10 days apart) after 12 hours without food, caffeine, and alcohol and 24 hours without exercise. Each visit followed double-blinded, randomized EGCG or cornmeal placebo supplementation (seven pills over 48 hours, 135 mg EGCG/pill). RMR and respiratory exchange ratio (RER) were determined using the ventilated hood technique for 45 minutes prior to consumption of a liquid mixed-composition meal providing calories equivalent to 40% of RMR. Energy expenditure (EE) and RER were then measured for the first 20 of every 30 minutes for five hours. RESULTS: All subjects (n = 9 males, n =7 females; age 25 ± 2 yrs, mean ± s.e.; 22.6 ± 1.8% body fat) were weight stable and were washed out from prior green tea or EGCG use for ≥ one month. Results are reported as placebo vs. EGCG. EGCG did not affect RMR or baseline RER (RMR: 1665 ± 84 vs. 1610 ± 89 kcal/day; p = 0.10; RER: 0.82 ± 0.01 vs. 0.83 ± 0.01; p = 0.29). EGCG did not affect the area under the TEF response curve, expressed as absolute postprandial EE (441,083 ± 22,436 vs. 429,350 ± 24,209 arbitrary units, A.U.; p = 0.22) or the absolute (58,104 ± 5,297 vs. 58,949 ± 5,672 A.U.; p = 0.88) or percentage (3,508 ± 263 vs. 3,647 ± 285 A.U.; p = 0.67) difference between absolute postprandial EE and baseline RMR. No differences between placebo and EGCG were observed for RER during TEF. CONCLUSION: These results indicate that, contrary to our hypothesis, short-term EGCG supplementation does not influence RMR or TEF in healthy adults. This suggests that reported positive benefits of green tea on energy balance are the result of increased physical activity EE and/or decreased energy intake.