BMI doesn't take into account muscle mass nearly enough, IMHO.
For example, in my own experience, when I weighed 150 at age 42 I wore a size 12 pant. Then I unfortunately gained more weight ending up at 185. I went on a strenuous weight lifting and higher protein plan, lost 10 pounds, gained probably 7 pounds of muscle and ended wearing a size 12 pants at 175 pounds. This wasn't really my plan, but it was how my body responded.
From what I understand about physiology, it's really important for aging people to keep the muscle intact and to increase if possible. Since I've been weight training I NEVER catch a cold, and I recover from injuries very quickly. If women, especially, build their muscles they protect their bones as well.
Another point is that culture often determines what we consider a "normal" body shape.
When I was in Tanzania this summer I was very interested to see that the Maasai men are very very thin, but not skinny thin. They have high muscle mass. They would be considered "underweight" by the BMI tables. That's a joke. They spend their days achieving the kinds of endurance feats that we do for sport in western countries. The Maasai women would probably be considered "overweight" in our culture but in Massai culture a woman's round figure is considered attractive. And these women eat the same food that the men do. And they do more of the work around the village. These are strong women. Also, traditionally these people are long lived, unless they get eaten by a lion, gored by a cape buffalo or stomped by an elephant. Now though the young men are going to the city and getting AIDs.
I have to say too that it was a very pleasant experience, as a middle aged woman with a "round" figure, to experience the admiration of and compliments from many Africa men who were much younger than I but who didn't think I was "old" and said I was "very beautiful."
Ok, back to the ole US of A. I know I'm overweight with a BMI of 29 and am working on changing that.
