Starving yourself causes your body to go into starvation mode which causes your metabolism to begin to slowly shut down.
When your metabolism slowly shuts down and then shuts down your body thinks that it won't get any food for awhile which helps to keep any fat or calories.
Starving yourself can also cause you to become sick,weak, lower your blood sugar levels and cause you to pass out and need hospitalization if you starve yourself long enough,
Starving yourself is never really a good way of losing weight. When trying to lose weight you should eat some food that is lower in calories and then exercise to burn off any excess calories.
Our bodies need food for fuel and without that fuel our bodies will not be able to keep up and may eventually lead to death if you starve yourself long enough.