The phrase "lazy people shit a lot" is slang, which is usually used to describe a person who is lazy, doesn't work hard when he needs to do something, and often makes excuses to avoid work or tasks, but at the same time, he often has more excretory needs.

The meaning of this sentence may come from life experience, because when a person needs to engage in manual labor or other work that requires concentration, the body's metabolism will accelerate and the number of urination may increase. People who are lazy and unwilling to work hard often find excuses to escape or delay in their work or tasks, and at the same time, due to their slow metabolism, they may urinate less frequently. So the phrase "lazy people shit a lot" means to satirize those who are lazy and don't work hard by using physiological phenomena.