Your body goes through a thing called 'kitosis'...thats where your supposed to eat < 20 g carbs/day for the first two weeks.
If you do this for a longer time...then your body tends to 'stall.' The key is to slowly start adding carbs to your diet to prevent stalls.
Good carbs...like fruits, not pasta, bread, or rice.
Thats my experience.
Also...drink lots of water...VERY key...supposed to be like 10 glasses a day.