Anaerobic metabolism produces energy faster but less ______ than aerobic metabolism.

Anaerobic metabolism is a pathway the body uses to generate energy without the need for oxygen. It is particularly useful during short bursts of intense activity, as it can produce energy quickly to meet the immediate demand. However, this type of energy production comes with a trade-off: it generates energy less efficiently compared to aerobic metabolism, which uses oxygen and is capable of sustaining energy production over a longer period.

When we refer to efficiency in this context, it encompasses the amount of energy produced in relation to the fuel consumed and the byproducts generated. While anaerobic metabolism can produce energy rapidly, it does so while yielding less usable energy per unit of fuel, primarily due to the production of lactic acid and other inefficiencies that arise from the breakdown of glucose without oxygen.

Given the context of energy production dynamics, "efficiency" correctly captures the distinction between the high-speed generation of energy in anaerobic processes and the more sustainable, long-term energy creation found in aerobic metabolism.