Anorexia Nervosa: Fasting and Starvation Brain Effects

Brain research in anorexia nervosa presents several challenges.

Current knowledge of cognitive function in anorexia supports impairment in set shifting and global brain processing or central coherence.

However, there are two issues that complicate understanding the underlying brain effects in anorexia nervosa.

First, individuals with anorexia nervosa often have additional anxiety and mood disorders. It can be difficult to tease out the specific effects of anorexia nervosa from the effects of these comorbid conditions.

Second, fasting and starvation are common metabolic issues in anorexia. These metabolic stresses can also influence brain function.

Sarah Pender and colleagues from University College London and Spain recently published a research study on the neuropsychology of starvation.

The key elements of their study included the following elements:

• Subjects: Healthy females recruited by poster in a university sample. Subjects were required to not have a lifetime history of any psychiatric disorder including anorexia nervosa.
• Measures: A test of set-shifting ability using a test called the rule-change task. A test of local versus global cognitive processing style. A second test of global processing known as the group embedded figures task.
• Metabolic status: Each subject was studied on the above measures after eating and following a period of 18 hours of fasting. 

The authors then compared performance on these neuropsychology tests in the fasting versus satiated state. The main findings from the study included findings in set-shifting and central coherence.

Set-shifting: Performance on set-shifting was not slowed or impaired in the fasting state compared to the satiated state. However, fasting appeared to increase the difficulty (or effort) to set shift.

Central coherence: During the fasting state, subjects shifted processing to a stronger local processing style and a weaker global processing style. This is consistent with reduced central coherence with fasting.

A relevant potential confounding variable in this type of task is the contribution of anxiety and depression in neuropsychological task performance.

I previously collaborated with Dr. Rebecca Marshall and other colleagues at the Laureate Institute of Brain Research in a study of neuropsychological function in a group of women with a variety of eating disorders. In this study, we found subjective anxiety ratings contributed to a significant about of variance in neuropsychological performance in eating disorders. Additionally, we found executive function impairment, a component of central coherence in 30 % of the clinical sample.

Pender and colleagues looked for effects of anxiety and depression in their study and did not find any confounding effects. Obviously, their sample was likely to only have minimal sub-clinical levels of anxiety/depression given the requirement for no current or lifetime psychiatric problem for enrollment.

The authors conclude even short-term fasting "might trigger weak central coherence, and thus play a role in maintaining behaviors characteristic of AN". 

The authors also note the brain effects of fasting, starvation and anorexia nervosa may have difficulty participating in psychotherapy. Psychotherapy requires a more global processing style to be effective.

Readers with more interest in this research can access the free full-text manuscripts by clicking on the PMID link in the citations below.

Photo of brain corpus callosum activated during right-left brain coherence is from an iPad screen shot from the 3D Brain app.

Follow the author on Twitter WRY999

Pender, S., Gilbert, S., & Serpell, L. (2014). The Neuropsychology of Starvation: Set-Shifting and Central Coherence in a Fasted Nonclinical Sample PLoS ONE, 9 (10) DOI: 10.1371/journal.pone.0110743

Billingsley-Marshall RL, Basso MR, Lund BC, Hernandez ER, Johnson CL, Drevets WC, McKee PA, & Yates WR (2013). Executive function in eating disorders: the role of state anxiety. The International journal of eating disorders, 46 (4), 316-21 PMID: 23354876