Well, yes that is true actually. But it's pretty irrelevant to most people on this blog losing weight.
You see, I did a bit of research with body builders and found there were various charts as to 'ideal' body builder weight against height. And those weight figures were surprisingly low.
And I took some examples based on my height and a large (rather than medium or small) frame and I took the highest figure I could find for weight.
And I found that even if I were pretty much rippling with muscle (and didn't have the fat) - as a competitive body builder - I would have a BMI of under 26. (Rather than my current 29.5!)
And also, if I were thus endowed with muscle, one look in the mirror would tell me that my slight overweight was due to muscle, not fat.
So please keep this notion in proportion. The normal range of BMI (18.5 to 25) can span something like 21 Kgs (well over 3 stone). So it accommodates people with fairly significant amounts of muscle.
If you're talking about BMI figures in the upper twenties and in the thirties, then you're talking about body fat. And if you've a BMI like that and have quite a bit of muscle, then you also have quite a bit of fat too.
Unless, as I've said before, you have a body like Mr Universe and even then your BMI isn't likely to be much above 26, if even that.
Sorry, if that upsets anyone.