OBJECTIVE: Severe and prolonged underweight can lead to a hypometabolic state and hormonal adaptations that reduce body temperature often found in Anorexia Nervosa (AN). However, the effect of these changes on brain temperature remains unclear. We aimed to investigate whether brain temperature remains stable despite lower body temperature in a severe underweight state, testing the hypothesis that the brain prioritizes its own energy needs during periods of food deprivation.

METHOD: We collected magnetic resonance spectroscopy (MRS) measurements from 30 female patients with acute Anorexia Nervosa (acAN) in a severe underweight state and 30 age-matched healthy female control participants (HC). MRS allows for a non-invasive assessment of brain temperature by calculating the difference between the temperature-independent peak of N-acetylaspartate (NAA) and the temperature-dependent peak of water (H20) in each voxel (ΔH20-NAA).

RESULTS: Our results showed no group differences in (ΔH20-NAA) between acAN and HC. This is supported by Bayesian hypothesis testing, providing strong evidence for the absence of lower brain temperatures in severely underweight states.

CONCLUSION: Our results are an indication that in a state of low energy availability, brain metabolism is prioritized.