Simplify the following text for a Grade 12 native English-speaking person.
Original: A study performed at Birmingham ( UK ) University , showed that average fat oxidation rates were 17 % higher after ingestion of green tea extract than after ingestion of a placebo .
Simplified: In a study performed at Birmingham ( UK ) University , it was shown that average fat oxidation rates were 17 % higher after drinking of green tea extract than after a placebo was used .