Are models too thin?

There has been considerable controversy recently following the decision by the Madrid Fashion Week to ban models below a certain size (BMI) from their catwalks. (This was followed more recently by a similar decision by the Clothes Show in Birmingham)

As far as I understand the beliefs behind this are twofold
(1) Such models have anorexia nervosa (may have anorexia nervosa?) and thus should not be working
(2) Such models, even if they don't have an eating disorder, set a bad example to impressionable young women who might go on to develop eating disorders

Now don't get me wrong. I think that the decision, in that it raises the profile of eating disorders and encourages debate, was probably a good one (although a naive one, as I'll go on to explain). But I would question both of the aims above. Firstly, it is not clear that all 'underweight' women have anorexia (or any other eating disorder). Some women are truly, naturally extremely thin. Weight, like other characteristic of humans, varies a great deal between individuals and it is as bad to automatically assume someone has an eating disorder because they are thin as it is to assume they do not have one because they are normal weight or overweight.
Of course, women can be underweight for other reasons, such as illness or drug misuse. Similarly, women who are not underweight may also have eating disorders (particularly bulimia nervosa, which is quite a bit more common than anorexia). Ignoring those women because their eating disorder is less easy to detect seems rather unbalanced.

I have spent many years attempting to 'diagnose' eating disorders, as part of my research and clinical practice, using various tools to help in this. Many, such as the Eating Disorders Examination, developed by Chris Fairburn and colleagues, are complex and time consuming to administer even after specialist training. The suggestion that one can 'diagnose' an eating problem simply by weighing someone is laughably naive.

The second supposed aim of the move, to reduce eating disorders in impressionable young women by stopping them from seeing emaciated models and trying to imitate them is also quite flawed. There is very limited evidence that exposure to to such models causes eating disorders (although it is possible that it may prove the 'last straw' in some particularly vulnerable women). What we do know is that exposure to such models reduces self esteem amongst young women, which may not lead to eating disorders, but is likely to just increase the amount of misery in the world. Most would agree that this is a bad thing, so from that point of view the move makes sense.

Finally, the idea that any model below the specified BMI will be 'given medical treatment' is another enormously naive idea. We know that people with eating disorders often have very mixed feelings about their condition and about recovery. The most conflicted amongst them are likely to be those who, despite the negatives of their condition (weakness, sensitivity to cold, osteoporosis, heart problems etc etc) are promised the highly valued rewards of money and celebrity status through their work as models. Are these women likely to accept the medical treatment offered, especially when it may compromise their career.

I'd like to see a whole range of body shapes and size represented in catwalk and magazine models, as well as different ethnicities and ages. Campaigns like Dove's Campaign for Real Beauty are very much along the right lines.