Anorexia nervosa (AN) is a psychiatric condition characterized by a fear of weight gain and reduced calorie intake, potentially leading to dangerous weight loss. It is estimated to affect 1-4% of women and is associated with a three-fold increased risk of premature mortality compared to individuals who have not experienced the condition.
AN can result in a 20-30% loss of skeletal muscle strength and size, in addition to fat loss. Treatment typically involves addressing the psychiatric aspects and restoring lost weight. Weight recovery is often defined clinically as a body-mass index of 18.5 or within 95% of an individual's age-predicted norm.
A recent study published in the Journal of Nutritional Physiology investigated whether muscle impairment persists after weight recovery in AN. The study, led by Megan Rosa-Caldwell, an assistant professor of exercise science at the University of Arkansas, utilized rat models.
Study Methodology
Eight-week-old rats were subjected to calorie-restricted diets for 30 days to model AN, a condition that typically manifests between adolescence and early adulthood in humans. Following the calorie restriction, cohorts of rats were examined after five, 15, and 30 days of recovery, during which they had ad libitum access to food. These recovery timelines were selected to simulate five months, 15 months, and two-three years of human recovery, respectively.
Key Findings
The researchers conducted tests to assess muscle mass, strength, and protein synthesis rates. A significant finding was an approximate 20% reduction in muscle size and strength, which did not improve during the shorter recovery periods (five and 15 days). Even after 30 days, when the animals had returned to their pre-restriction weight and matched healthy control rats in weight, an overall decrease in muscle quality persisted, resulting in lower muscle force per unit of muscle mass.
Evidence of changes in protein synthetic signaling was also observed, with "anabolic signaling cascades appear[ing] attenuated following long-term recovery from AN," indicating a weakened capacity for muscle building.
Implications
Rosa-Caldwell stated that musculoskeletal complications may persist longer than generally understood and should be considered in treatment approaches for individuals with AN. The researcher also noted that due to the controlled nature of the experiment, the effects of AN in rats might be less severe than in humans, where the condition can involve prolonged struggle and relapse. The study suggests a need for interventions to facilitate faster muscle recovery.