How would consuming less than 1200 calories per day impact metabolism?

By consuming less than 1200 calories a day it impacts a person’s metabolism by slowing it down and forcing the body to break down its own tissues if it is not receiving sufficient calories to withstand vital functions. There are slight side effects of a less than 1200 calories which are faintness, tiredness, irregular periods, and unsteadiness. Some major side effects might have impact on the gallbladder, gout, excruciating inflammation of the joints and also death.