Medical experts usually say the average person can live for 4 to 6 weeks without food. The amount of time someone can go without water is much shorter, roughly a week (or less).
Your employer can force you to take leave at a particular time as long as they give you at least two weeks' notice. However, it is common for employer and employee to come to an agreement about the timing of annual leave. If you put in a request for leave, your employer has to have a good reason to refuse it.
Employees who request an FMLA leave must be employed by a covered employer, which is a private sector employer that employs 50 or more employees for at least 20 work weeks in the current or previous year; and all state, local and federal agencies and educational agencies.