My best friend is clinically obese. Her diet is fine, it's lack of exercise and medication that's the problem. Her diet is a model of what it should be but she is still overweight.
I have another friend who smokes, drinks, hardly ever exercises, eats an appalling diet and is a size 6 (if that).
I am quite happy to accept that body weight is in part a matter of genetics. Some people are naturally slim, some naturally more solid. I find it appalling that someone who is 9 stone can be considered overweight by the media. From a feminist perspective it annoys me even more, since women are subjected to far greater scrutiny than men when it comes to body weight.
However, within a certain amount of weight either way, I think it's silly to pretend that any size is perfectly ok. Being more than a couple of stone over or underweight carries serious health consequences. I wouldn't dream of punishing people or telling them what to do because it's a basic human right to do with your body as you will, but acceptance and tolerance is not the same as endorsement.
i think we've got a completely backwards approach to nutrition in this country though. We've lost the art of preparing a balanced diet on a low budget. Eating healthily costs time and money unless you have quite a lot of knowledge about food and where to get it from. And it needs to be balanced by regular exercise. You can have a great diet but if the only walking you do is around your house and to your car you're still way more likely to suffer from cholesterol and high blood pressure, etc.
One way we could tackle this is through sensible home economics classes (for both genders of course). I am horrified that my local secondary school has HE classes that each week involve ingredients to the value of about £10-£15. For one dish! My diet is excellent and I can feed 3 of us for about 3-4 days on that.
I can't help feeling that if food was more about nutrition as part of an overall healthy lifestyle than about appearance and being 'good', a lot of the problems would magically disappear.