Causes- Biological

There is much debate over whether the cause of an eating disorder is biological or psychological. There are reasons to believe science plays a part, however the main consensus appears to be that such factors play a contributing role and are not the sole triggers.  

Neurotransitter levels

Many sufferers have been found to have an imbalance in key neurotransmitters such as dopamine and serotonin. These also play a part in other mental health disorders such as depression, schizophrenia and obsessive compulsive disorder. Dopamine is also believed to have a role in addiction (hence the addictive nature of an eating disorder). Lowered serotonin levels are a cause of depression. Eating disorder sufferers often battle depression amongst their other symptoms. Serotonin levels rise on eating and increase satiety. This suggests that anorexics may have abnormally high levels of serotonin, whilst bulimics and binge eaters have low levels.

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Damage to the Hypothalamus

Damage to this part of the brain can have an effect on the arcuate nucleus, and therefore can cause a disruption in the release of neuropeptides αMSH and CART (anorextic peptides whuch inhibit feeding behaviour) and Neuropeptide Y, AgRP, MCH and orexin (orexigenic peptides which stimulate feeding). An inbalance in these peptides can present itself in the symptoms of an eating disorder. 

Leptin

In bulimia and binge eating disorder, sufferers were found to have normal levels of leptin, however it has been suggested that there is a problem with this leptin crossing the blood brain barrier and therefore signalling to the brain that eating can stop.