It really is sad.
I started yoga about a year and a half ago for my back health and most of the classes are younger females. I would say if there are 15 girls in the class, 12 of them are over weight. The lightest of which would be right on the national average of about 170lbs and about 5'4" in height and many of them much bigger.
And because they are young the weight does not look terrible for most of them YET, but it will mean all sorts of problems (not just unsightly) as they age.
there are typically 4-5 guys in the classes and they tend to never be overweight. I recall one 'chubby' guy, but over all the guys are in good shape.
I think for guys, typically the weight hits at a later age. Women seem to get hit very early if they do not practice any disciplines young.