What is the origin of the idiom "lean and mean" and when to use it?

The origin of the phrase "lean and mean" is not definitively known, but it is believed to have emerged in the late 20th century. The phrase "lean and mean" is used to describe something or someone that is highly efficient, focused, and effective. It can be used in business, sports, or fitness contexts to convey a state of optimal performance and a streamlined approach to achieving desired results.