Want to be unhealthy fast? Try a crash diet. Cutting down on calories too fast and too low can actually increase your chances of hurting yourself. There is nothing "wrong" with a calorie restricted diet however not all calories are create equal. Be certain you are getting the nutrients your cells need.
Eating very little and getting very few nutrients can actually increase your metabolism and decrease the strength of your bones. When you are on a weight loss plan be certain to incorporate weight training as it will increase your metabolism and strengthen your bones. Remember that no matter what method you use to lose weight, if you do not alter your attitude,beliefs and habits--it will only be temporary. 5% of people who lose weight by any given method will keep it off for the rest of their lives. The rest will continue the cycle. For real change both your physical and mental self should exercise and eat healthy.