2006 Toyota Yaris Catalytic converter

The silencer do not throw any oil and did not observe any leakage but the oil level in the engine is dropped by 200ml after 1000km drive. Some people say the choked catalytic converter can effect the engine performance. Can the blockage of catalytic converter affect the engine performance. Is there any chance of the choking of catalytic converter? The engine thrust as observed from the silencer is low as compared with the cars without a catalytic converter.