Logging body measurements

The app asks the user to log weight and body fat percentage. Since I don't have a reliable way of measuring my body fat, I have left the box blank. I have dropped weight, but the app says that since I haven't logged my body fat, I might be losing muscle instead of fat. My waist has shrunk so I know that I have lost body fat, but there is no way to tell the app that.

How about adding a box for some body measurements? After all, health wise the waist measurement is more important than fat percentage, and you can easily measure your body measurements, but getting reliable body fat percentage requires some speciality equipment, or you have to pay to get it measured. I have one of thise cheap electric measuring devices, but it is far from reliable. 

Even if you are not trying to lose fat, it still could be useful to record the measurements.