I guess it depends on how the studies were conducted (I haven't looked). They may well take steps to eradicate this problem. However, I suspect you are right

I guess it depends on how the studies were conducted (I haven't looked). They may well take steps to eradicate this problem. However, I suspect you are right and - in actual fact - this may really be what the studies are concluding: that parents of overweight children do not see the problem because the average they see around them is not medically-healthy normal. It would be interesting to see the average weights of children in the study areas to see how much the theory stands. It would also be interesting to see a similar survey that asked whether they thought their child was within the healthy bounds (i.e. no classifications like "overweight" where they could draw comparisons).