The effects of catechin rich teas and caffeine on energy expenditure and fat oxidation: a meta‐analysis

Different outcomes of the effect of catechin‐caffeine mixtures and caffeine‐only supplementation on energy expenditure and fat oxidation have been reported in short‐term studies. Therefore, a meta‐analysis was conducted to elucidate whether catechin‐caffeine mixtures and caffeine‐only supplementation indeed increase thermogenesis and fat oxidation. First, English‐language studies measuring daily energy expenditure and fat oxidation by means of respiration chambers after catechin‐caffeine mixtures and caffeine‐only supplementation were identified through PubMed. Six articles encompassing a total of 18 different conditions fitted the inclusion criteria. Second, results were aggregated using random/mixed‐effects models and expressed in terms of the mean difference in 24 h energy expenditure and fat oxidation between the treatment and placebo conditions. Finally, the influence of moderators such as BMI and dosage on the results was examined as well. The catechin‐caffeine mixtures and caffeine‐only supplementation increased energy expenditure significantly over 24 h (428.0 kJ (4.7%); P < 0.001 and 429.1 kJ (4.8%); P < 0.001, respectively). However, 24 h fat oxidation was only increased by catechin‐caffeine mixtures (12.2 g (16.0%); P < 0.02 and 9.5 g (12.4%); P = 0.11, respectively). A dose‐response effect on 24 h energy expenditure and fat oxidation occurred with a mean increase of 0.53 kJ mg−1 (P < 0.01) and 0.02 g mg−1 (P < 0.05) for catechin‐caffeine mixtures and 0.44 kJ mg−1 (P < 0.001) and 0.01 g mg−1 (P < 0.05) for caffeine‐only. In conclusion, catechin‐caffeine mixtures or a caffeine‐only supplementation stimulates daily energy expenditure dose‐dependently by 0.4–0.5 kJ mg−1 administered. Compared with placebo, daily fat‐oxidation was only significantly increased after catechin‐caffeine mixtures ingestion.