It's a common cry; "I'm eating practically nothing, I'm starving, why am I not losing weight?", most usually heard part-way through a weight loss regime that involves reducing calorie intake.
Quite simply, the human body is pretty clever. Have you seen those documentaries on anorexics who survive on 600-800 kcals a day? They, even though they weigh very very little, exist on way below the number of calories required to maintain their weight and yet it takes significantly longer for them to lose any further weight than it should do given the deficit they're in. OK, they're a pretty extreme case, but it does illustrate what the human body can do when put under those kinds of conditions.
If you restrict calories significantly for a period of time (the length of which appears to be dependant on the individual) your body starts to become more creative about using those calories. The one I noticed more than anything else while I was losing weight was that I got cold. Not just because I had less fat to keep me warm but because my metabolism slowed down! My body decided that rather than using up fat (oh yes, and muscle too!) to fuel my needs, it would cut down on generating warmth. It wasn't a huge amount of temperature drop and I was still losing some weight but there was certainly a trade off there and I got oh so very very cold and had to wear many layers more than I was used to just to stay warm.
Other ways your body will adjust to the continued lower calorie intake is to stop laying down as much glycogen for ready energy for your muscles, so you'll get fatigued more quickly when doing anything physical; like getting out of bed in the morning perhaps...