1.
The effect of caffeine, green tea and tyrosine on thermogenesis and energy intake.
Belza, A, Toubro, S, Astrup, A
European journal of clinical nutrition. 2009;(1):57-64
Abstract
OBJECTIVES To investigate the effect of three different food ingredients tyrosine, green tea extract (GTE) and caffeine on resting metabolic rate and haemodynamics, and on ad libitum energy intake (EI) and appetite. METHODS Twelve healthy, normal weight men (age: 23.7 +/- 2.6 years, mean +/- s.d.) participated in a four-way crossover, randomized, placebo-controlled, double-blind study. Treatments were administered as tablets of 500 mg GTE, 400 mg tyrosine, 50 mg caffeine, or placebo, and were separated by >3-day washout. The acute thermogenic response was measured in a ventilated hood system for 4 h following ingestion. Blood pressure, heart rate (HR), and subjective appetite sensations were assessed hourly and ad libitum EI 4 h post-dose. RESULTS Caffeine induced a thermogenic response of 6% above baseline value (72 +/- 25 kJ per 4 h, mean +/- s.e.) compared to placebo (P<0.0001). The thermogenic responses to GTE and tyrosine were not significantly different from placebo. Tyrosine tended to increase 4-h respiratory quotient by 1% compared to placebo (0.01 +/- 0.005, P=0.05). Ad libitum EI was not significantly different between treatments but was reduced by 8% (-403 +/- 183 kJ), 8% (-400 +/- 335 kJ) and 3% (-151 +/- 377 kJ) compared to placebo after intake of tyrosine, GTE and caffeine, respectively. No significant difference in haemodynamics was observed between treatments. CONCLUSIONS Only caffeine was thermogenic in the given dose and caused no haemodynamic side effects. The sample size was probably too small to detect any appetite suppressant properties of the treatments. Further investigations are required.
2.
Effect of moderate intakes of different tea catechins and caffeine on acute measures of energy metabolism under sedentary conditions.
Gregersen, NT, Bitz, C, Krog-Mikkelsen, I, Hels, O, Kovacs, EM, Rycroft, JA, Frandsen, E, Mela, DJ, Astrup, A
The British journal of nutrition. 2009;(8):1187-94
Abstract
Green tea may stimulate energy metabolism; however, it is unclear if acute effects are caused by specific catechins, caffeine or their combination. The objective of the present study was to examine the separate and combined effects of different catechins and caffeine on energy expenditure (EE) and fat oxidation over a single day. Fifteen healthy, normal-weight males received capsules containing placebo, caffeine alone (150 mg), or caffeine plus a catechin mixture (600 mg) enriched in either epigallocatechin-3-gallate (EGCG), epigallocatechin or a mix of catechins, in a randomised cross-over double-blinded design. On each test day EE, respiratory quotient (RQ) and substrate oxidation were measured under sedentary conditions in a respiratory chamber for 13.5 h. We found no significant treatment effect on EE (P = 0.20) or RQ (P = 0.68). EGCG with caffeine insignificantly raised EE and fat oxidation v. caffeine-only and placebo (EE 5.71 (SE 0.12) v. 5.68 (SE 0.14) v. 5.59 (SE 0.13) MJ/12.5 h, respectively; fat oxidation 84.8 (SE 5.2) v. 80.7 (SE 4.7) v. 76.8 (SE 4.0) g/12.5 h). Catechin/caffeine combinations at these dosages and mode of application had non-significant acute effects on EE and fat oxidation. The maximum observed effect on EE of about 2 % could still be meaningful for energy balance over much longer period of exposure. However, higher short-term effects reported in the literature may reflect variations in green tea extracts, added caffeine, or synergies with physical activity. The specific mechanisms and conditions that may underpin observed longer-term benefits of catechin-enriched green tea consumption on body composition remain to be confirmed.
3.
Effect of chewing gum containing nicotine and caffeine on energy expenditure and substrate utilization in men.
Jessen, AB, Toubro, S, Astrup, A
The American journal of clinical nutrition. 2003;(6):1442-7
Abstract
BACKGROUND Nicotine replacement therapy limits weight gain after smoking cessation. This finding is partly attributable to the thermogenic effect of nicotine, which may be enhanced by caffeine. OBJECTIVE We assessed the acute thermogenic effects of chewing gum containing different doses of nicotine and caffeine. DESIGN This randomized, double-blind, placebo-controlled, crossover study included 12 healthy, normal-weight men (aged 18-45 y). Energy expenditure was measured with indirect calorimetry before and 2.5 h after subjects chewed each of 7 different types of gum containing the following doses of nicotine/caffeine: 0/0, 1/0, 2/0, 1/50, 2/50, 1/100, and 2/100 mg/mg. RESULTS The thermogenic responses (increases over the response to placebo) were 3.7%, 4.9%, 7.9%, 6.3%, 8.5%, and 9.8%, respectively, for the gums containing 1/0, 2/0, 1/50, 2/50, 1/100, and 2/100 mg nicotine/mg caffeine (P < 0.05 for all). Adding caffeine to 1 and 2 mg nicotine significantly enhanced the thermogenic response, but changing the caffeine dose (from 50 to 100 mg) did not change the thermogenic effect. None of the combinations changed the respiratory quotient compared with placebo, which indicates that glucose and fat oxidation rates were increased to a similar extent. Side effects occurred only with 2 mg nicotine. CONCLUSIONS One milligram of nicotine has a pronounced thermogenic effect, which can be increased by approximately 100% by adding 100 mg caffeine. Increasing the nicotine dose to 2 mg does not increase the thermogenic effect but produces side effects in most subjects. Caffeine may be useful in preventing weight gain after smoking cessation if its thermogenic effect can be used to enhance nicotine's effect on long-term energy balance.