Hi:

Many people do not eat any calories on their diet days and they generally lose bit more weight than those that do. Some people will warn of some kind of ‘starvation mode’, or similar concept, that purportedly stalls weight loss until you start eating more calories. However, if there is a ‘starvation mode’, all scientists agree that the impact of it cannot be measured and that it does not prevent weight loss. At most, it lowers a person’s TDEE. As you are eating quite a bit less than usual, you are taking in fewer vitamins/minerals from food and you may want to try a good supplement (emphasis on good).

Here is how the ‘numbers’ work: http://thefastdiet.co.uk/forums/topic/tdee-for-the-curious-or-why-dont-i-lose-weight-faster/

Good Luck!