Self-injury (such as cutting or burning oneself) is fairly common amongst people with eating disorders- approximately 25% to 45% of people with eating disorders self-injure, and approximately half of those who self-injure also have eating disorders (full article here). Many people report a sense of dissociation while self-harming, a desire to turn emotional pain into physical pain (ie, "real" pain), and also that this behavior reduces anxiety. Whether self-harm is from issues relating to impulse control, a more compulsive pattern of behavior, or something else entirely, the amount of overlap between self-injury and eating disorders is significant.
An interesting new paper from the journal Psychoneuroendocrinology looked at the relationship between self-injury and glucose metabolism in women with eating disorders, and what they found was significant. Women engaging in self-harm behaviors were given an oral glucose tolerance test, in which they were asked to drink a sweet solution to measure how the body handles sugar. The self-harming women who also had an eating disorder had higher levels of blood glucose after the test, but also higher levels of a hormone called glucagon.
Glucagon is essentially insulin's opposite: when the blood sugar is low, the pancreas secretes glucagon to prod cells into breaking down long chains of carbohydrates called glycogen into small sugars that can be released into the bloodstream and readily used by the body. When blood sugar rises after a meal, the pancreas secretes insulin, which stimulates cells to pull excess sugars out of the bloodstream and store them as glycogen for a rainy day*.
Besides low blood sugar, several other factors can stimulate the release of glucagon, including epinephrine (aka adrenaline), which is involved in the fight or flight response. Though I was unable to find any specific studies linking high levels of epinephrine and self-injury, it's certainly plausible to think that people who self-harm would have higher levels of epinephrine, especially right after an incident where such behavior occurs. Alternately, if high levels of glucagon also stem from high levels of epinephrine, the sufferer may be caught in a cycle of self-harm during episodes of low blood sugar.
For instance, a common pattern in those who binge and purge is binge-purge-self harm, where the self-harm typically occurs after the completion of the binge/purge cycle. After a binge, blood sugar goes up and glucagon levels go down. After a purge, blood sugar goes down, and glucagon and epinephrine levels go up.
No one knows at this point where the relationship between self-harm and glucose metabolism lies on the cause/effect scale. Certainly there is a feedback cycle between all of these systems. But one good point to keep in mind is the importance of helping sufferers regulate blood sugar levels by frequent meals and snacks that involve complex carbohydrates, proteins, AND fats. Food is medicine for the eating disorder, but it also might be true for self-injury.
*Aren't you glad I paid attention in my 8am biochem lecture 10 years ago?
(cross-posted at ED Bites)