MFP "__kg in 5 weeks" ?

Hi all! I was wondering if any of you know just how accurate the "you will lose __kg in 5 weeks" thing is after you've logged your diary for the day... I'm currently at 54.5kg, and according to MFP if I eat 2000 calories a day then I will weigh 53kg in 5 weeks.. I just find it hard to believe that it would happen (I didn't include exercise or anything!)