I think the thing is that lean muscle actually weighs more than fat does (volume-volume). So, two people who both weigh 120 pounds and are the same height, one lean and one fat, would get the same exact BMI calculation but actually have very different percentage body fat. So, it's very possible to increase your fitness, decrease your body fat, add lean muscle, and see no real change on the scale or your BMI calculation.
At my next checkup I'm going to ask my doctor if she has another way to estimate/calculate my body fat. :rolleyes:

