Did you really mean 30 days or 3 days?
Why on Earth would you want to starve yourself for a month? Do you not have a job or other things which you need to do which require you to move around and use energy which can only be provided by food? It sounds positively dangerous to me.
Even if it's a typo and you meant 3 days it still sounds mad, the page I’ve just googled on the subject says you should not attempt anything this extreme for more than 24 hours without medical supervision. Starvation diets don’t work, your body will slow your metabolism down to conserve whatever fuel it has got left, then as soon as you start eating again you'll put all the weight straight back on. Far better would be to reduce your daily food intake gradually, e.g. reduce portion sizes at mealtimes, or cut out snacking, or eat more green veg and less carbs etc etc. One step at a time, this would not only be safer it would be more sustainable and easier to stick to. If you need to lose weight you can’t just “go on a diet” for a few weeks and then go back to normal, you have to make changes that you can keep forever, and then the weight should stay off.
