Rate of Weight Loss, not Underweight Status, a Marker of Instability in Anorexia

Rapid weight loss may be a marker for clinical instability among adolescents with anorexia nervosa (AN). This systematic review and meta-analysis was published in the Journal of Eating Disorders

The underweight status and speed of weight loss may be markers of disease severity in eating disorders. As early identification of symptoms and appropriate severity stratification are important for illness management, the aim of this study was to evaluate current data on markers for instability in AN.

Investigators at London Metropolitan University in the United Kingdom searched publication databases through September 2022 for studies of medical instability in AN. A total of 9 articles were included in this review.

All studies included adolescents with AN or atypical AN and reported medical instability outcomes of heart rate, blood pressure, temperature, and serum phosphorous levels. The studies included between 29 and 1310 patients and most patients were girls or women.

In 1 study, 35% of patients presented with medical instability, including bradycardia, hypotension, dehydration, and hypothermia and half (51%) required hospital admission. Almost half (42%) of patients were medically unstable without being underweight. Two additional studies found similar trends, that medical instability was not necessarily related with being underweight.

Hypophosphatemia was reported to be directly proportional to the degree of being underweight and patients who developed hypophosphatemia were more malnourished than those who did not develop hypophosphatemia (P =.02).

A total of 3 studies could be included in the meta-analysis of underweight status. The degree of being underweight was associated with lower blood pressure (mean difference [MD], -5.89; 95% CI, -7.81 to -3.97 mmHg; I², 0%; P <.00001) but not lower heart rate (MD, 0.94; 95% CI, -0.87 to 2.75 bpm; I², 0%; P =.31), temperature (MD, -0.14°C; 95% CI, -0.53°C to 0.24°C; I², 82%; P =.46), or amount of weight loss (MD, -0.30; 95% CI, -0.71 to 0.12 kg; I², 54%; P =.16).

For weight loss, a randomized controlled trial reported that greater speed and magnitude of weight loss associated with decreased heart rate and serum phosphorus levels. In addition, lower serum phosphorus was associated with more rapid weight loss (P =.04) over a longer time period (P =.001). Another study reported that greater total weight loss and greater recent weight loss were both associated with decreased heart rate and bradycardia (all P ≤.006). Of note, 1 study reported that patients with a historically greater BMI had a higher total decrease in BMI than individuals who were not historically overweight (P =.0001).

The major limitation of this review was the small number of relevant studies.

The review authors concluded, “In our review, findings indicated that greater magnitude and speed of weight loss predicts physical complications requiring [hospitalization], independent of degree of underweight. In addition, adolescents of a higher premorbid weight were found to have greater weight loss than those of a lower weight.”