Researchers are exploring genetic and parenting roles in eating disorders. By Marc Wilson.
It is something of a paradox that people in the throes of a serious eating disorder will swear that they're overweight.
This is often hard for others to make sense of. Surely, if your Body Mass Index (BMI) is less than 18.5 (objectively underweight) and everyone else looking at you thinks you're skinny as, you must be lying?
Up to 4 per cent of the population, disproportionately women, experience the symptoms of anorexia nervosa at some point in their lives, and a further 4 per cent experience bulimia.
Bulimia is characterised by episodes of overeating and purging. Anorexia involves abnormally low body weight, but also an intense fear of gaining weight and a distorted perception of one's body.
Although we assume that what we see in the mirror is what the mirror actually sees, that might not be the case if one is seriously underweight. And it goes beyond visual impairment.
People with eating disorders typically display both body-image disturbance and problems in what is called interoception – how they perceive and interpret their bodily sensations.
This may include difficulties identifying things by touch and an impaired ability to use their bodies effectively for their size – because they perceive their bodies as larger than they are, they move in ways that reflect that incorrect perception.
It's not just eating-disorder sufferers who see themselves as larger (or different) than reality. In fact, people are more likely to develop eating disorders if they experience body-image disturbance, and the greater the disturbance, the tougher the recovery when someone does have an eating disorder. Body-image disturbance can also persist some time after "recovery".
So, eating disorders often involve a perceptual disturbance and can also involve mild impairments of cognition (thinking).
Marion Roberts, a clinical psychologist and University of Auckland senior lecturer, has for more than a decade been researching the cognitive challenges that may co-occur with eating disorders.
Among other things, her research, with colleagues from around the world, shows that people with eating disorders perform differently from "normal" participants on tasks such as the – take a deep breath – Rey-Osterrieth Complex Figure Test.
The Rey Figure Test invites participants to copy a line drawing (it looks like a complicated rocket ship on its side), first when they have the original diagram in front of them, and then from memory.
It's not necessarily how accurately you copy the diagram, but the order in which you copy the various bits. Basically, people with eating disorders show particular strength around the local detail, but weaknesses in the big picture.
This preoccupation with the detail probably goes with being able to single-mindedly focus on food, and not eating it.
Fascinatingly, parents of people with eating disorders show a greater similarity to this rigid cognitive style than parents with family members without these illnesses.
Roberts and colleagues speculate that this might contribute to a familial modus operandi that unwittingly reinforces maladaptive behaviours through more-rigid-than-usual parenting and an inability to see the bigger picture.
We don't fully understand eating disorders yet, but we know that there's some kind of genetic component. If you have a family member diagnosed with one, you're more likely than average to experience one yourself, for example, and it turns out that family members of people with eating disorders also perform differently in the Rey test.
So, back to the beginning. No, that super-skinny person you know isn't making it up or rubbing it in when they look in the mirror and worry about what they see.