It has been widely held that the catechin EGCG is responsible for the beneficial effect of green tea on weight loss. Green tea and green tea extracts increase thermogenesis and fat oxidation rates, but studies had not confirmed whether it was the EGCG that caused these improvements.

In order to isolate the effect of EGCG on weight loss paramaters, 6 overweight men were given a large dose of EGCG over two days. No increase in metabolic rate was observed, but their respiratory quotient showed a dramatic increase in fat oxidation.

PMID: 17906192