[jimmaswell]

For an average height, the span between the lowest non-over-or-underweight weight and the highest is a lot more than 20 pounds, and being a bit into the overweight range doesn't automatically make you unhealthy either.

chart: http://www.vertex42.com/ExcelTemplates/Images/body-mass-inde...

[zumu]

Don't forget there's a difference between weight from fat and weight from other sources (muscle, bone, water, etc).

[mrep]

If you lift weights, I wouldn't use body mass indexes.