Body composition is more helpful than BMI in tracking antidepressant side effects: study

While weight gain is a well-known side effect of antidepressants, new research from the University of Oslo suggests that only monitoring a patient's body mass index (BMI) fails to capture potentially harmful changes in body composition associated with an increased risk of cardiometabolic disease. The results of the study, published in Obesity, demonstrate that muscle volume and fat distribution biomarkers derived from an MRI scan could be more useful data points in assessing an individual's response to the medication, and to guide the development of new antidepressants. 

Antidepressants are the most commonly prescribed psychotropic medications, with a prevalence of 10% to 13% in adults, according to the researchers. Consequently, it has become even more important to track the fat distribution and muscle composition of antidepressant users.  

For the study, researchers measured the BMI of 1,224 patients taking selective serotonin reuptake inhibitors (SSRIs) and 568 patients taking tricyclic antidepressants (TCAs), and also assessed each patient's body composition using whole-body MRI-based technology developed by AMRA Medical. 

From the MRI scans, AMRA determined personalised "z-scores" for each study participant based on visceral, subcutaneous and liver fat levels, as well as muscle volume, to predict cardiometabolic risk based on fat distribution patterns. The US and Canada approved AMRA's MRI-based muscle assessment tech in 2022.

Findings revealed that SSRI users had more visceral fat, smaller muscle volume and higher muscle fat infiltration compared with matched controls. Women experienced a higher increase in BMI over time than men; however, overall, men had unhealthier body composition profiles, as measured by z-scores. Male SSRI users were also at increased risk for heart disease. TCA users of both sexes had lower muscle volume and were at increased risk for developing type 2 diabetes.

Psychotropic drugs are a new frontier for AMRA, which initially focused on metabolic and neuromuscular disease areas. In a study published in March, z-scores predicted how Eli Lilly's GLP-1/GIP agonist Mounjaro (tirzepatide) would impact patients with type 2 diabetes, which helped establish biomarkers that could help forecast treatment effects during future metabolic drug development. Another study in April explored how Novo Nordisk's GLP-1 agonist Victoza (liraglutide) affects thigh muscle fat and muscle composition in adults with obesity.

Now that the company has expanded its technology to neuropsychiatric drugs with metabolic effects, it hopes the current study can serve as a foundation for future research.