Ketosis is a condition associated with chronic starvation. When you go on an extreme diet the body loses weight at first, but eventually the body goes into "starvation mode". It is a survival mechanism. The body thinks that there is a famine and it is starving. Your metabolism slows down, and you burn less calories throughout the day. If we diet without exercise, we do lose fat, but we also lose a lot of muscle, which is not good. So, the smart thing to do is to follow a healthy, sensible diet that is low in high-calorie foods and to engage in vigorous cardio exercise, such as running, several times per week. Expect to lose about 1 - 2 pounds of fat/week.