I can only access the abstract, but this is fascinating: "[t]he highest centile increased by some 18 to 22 units in the course of the century". An increase of 22 units runs the gamut of possible BMI values [1], from severely underweight to obese class 2. It's equivalent to gaining 170 lbs (for a 5' 11" person).
[1]: http://en.wikipedia.org/wiki/Body_mass_index