BMI obviously works for the majority, i.e. those who have not gone through a period of concentrated muscle development (gives a high BMI) and those who go through a period of concentrated fat loss (gives a low BMI). For instance, when I was training I would have been over 25, but now I have stopped and lost some of the muscle I am in a healthy weight range.
A better indicator is % body fat, which is not as accessible and can vary depending on the quality of instrument doing the reading (the @home scales r scchit), but is better nonetheless.