Prana, if you are at 21% body fat, then you are already at the lower end of average. To get down to 16-18% would be where athletes are. That takes a lot more then diet, including a fairly intense workout program. If you want to push your body fat lower in a healthy manner, then it is going to take time in the gym with weights. You might check out the body for life program, there is a forum on here about combining BFL with low carb.