# Electrical impedance myography as a marker of muscle mass in rats with simulated Anorexia Nervosa

## TL;DR

This study shows that electrical impedance myography can non-invasively track muscle mass changes in rats with simulated anorexia nervosa and during recovery.

## Contribution

The study demonstrates that EIM is a viable, non-invasive method to assess muscle mass changes during simulated anorexia and recovery phases in rats.

## Key findings

- EIM parameters detected muscle mass changes during simulated AN and recovery.
- Resistance parameter showed the strongest correlation with gastrocnemius muscle mass.
- Maximal tetanic plantar flexion did not correlate with EIM parameters.

## Abstract

Anorexia Nervosa (AN) is characterized by a severe reduction in caloric intake resulting in substantial weight loss. Methods to evaluate muscle loss specifically during AN or following a weight recovery intervention are difficult to administer and expensive.

To evaluate the utility of electrical impedance myography (EIM) to assess changes to muscle mass during simulated AN and different durations of weight recovery in rats.

Female Sprague-Dawley rats (n=11/group, total of 66 rats, 8 weeks old) were divided into simulated AN or healthy control conditions. Simulated AN included 30 days of 50–60% food restriction. Following AN intervention, rats were further subdivided into recovery cohorts which included five, fifteen, or thirty days of ab libitum food consumption to elicit weight gain. EIM was assessed at various stages of weight loss and recovery and correlated to metrics of muscle mass.

Various EIM parameters detected changes in muscle mass both during simulated AN and following weight restoration. The resistance parameter produced the most consistent results during simulated AN and following various stages of weight recovery. Moreover, the resistance parameter had the highest correlation with gastrocnemius mass (r = ~0.50, p<0.05). Maximal tetanic plantar flexion was also analyzed but did not correlate with any EIM parameters.

EIM can non-invasively detect changes to muscle mass during AN and following various states of weight recovery.