we notice the obese family and assume the obese parents are passing their 'bad eating habits' to their kids. But if we saw a thin parent with a big kid, we don't attribute that sort of 'vice' to the parent.
yes i would assume the obese parents are passing their bad eating habits or poor lifestyle choices etc down to their growingly obese kids - i think its a fair assumption? however if i saw a more normal sized parent with an overweight kid, i would still have the same assumption of the parent (some people can be couch potatoes and live on fried food and still have a great metabolism).... what i'm try to say is i put the parents at fault if their kids are unhealthily overweight...

i guess i notice the entire fat families because it seems to be so much more severe (their obesity)