I will second, or third, or whatever the number may be what Brad has said. You might loose weight with a sub 1000 calorie a day diet, but I doubt long term you are going to be happy with the results. You might end up thin (or at least thinner), but how do you feel? Whats your energy level like? Can you keep up with the kids despite the fact you are no longer carrying the weight?
Also agree that you have to push your body beyond whats comfortable.. If it doesn't hurt, your not doing it hard enough.