Anya, yes but, don't forget that a third of the population are at the other end of the spectrum, the BMI calculation is over estimating the proportion of lean muscle to fat and telling them they are in the recommended range when actually they still have too much fat on their body. This is exactly the point crun makes.
As part of a healthy living promotion at work some years ago my body fat was measured by the more accurate method of using calipers to measure the thickness of folds of fat on my body. On the basis of that I was told I needed to lose about half a stone to reach a weight where I was not carrying excess fat. The BMI formula tells me that I am in the approved BMI zone when I weigh a stone more than the weight I was recommended to reach then - and the weight recommended was the upper limit I should reach
Fortunately I use my eyes to gauge a healthy weight. I can see that when my BMI is at the top end of the recommended range I have rolls of fat on my stomach and midriff so I try to stick to the weight recommended all those years ago. That weight gives me a BMI close to the lower level for a healthy BMI, but is nevertheless the maximum I should be.
That's fine for me, I understand the statistics and can look at the context but many people just think that providing they are in the recommended BMI range then everything is OK, when for 1 in 3 they are still carrying too much fat on their bodies and could still, quite unwittingly, be putting their health and longevity at risk.
Those over the BMI because they have a higher than average proportion of lean muscle to fat then get harassed and told off for a problem they do not have.