Both new weight loss drugs and bariatric surgery can improve body composition in patients with obesity, according to a study conducted by researchers at Vanderbilt Health. The research found that these interventions result in a moderate reduction of fat-free mass, which includes lean muscle, along with a substantial decrease in fat.
The study highlights the significance of body composition changes for health outcomes. Higher levels of fat mass are linked to increased mortality risk from obesity-related diseases such as cardiovascular events, while higher fat-free mass is considered protective against mortality.
The findings were published on January 9 in JAMA Network Open. The study was led by Danxia Yu, PhD, associate professor of Medicine in the Division of Epidemiology, and Jason Samuels, MD, assistant professor of Surgery.
Researchers analyzed electronic health records from 1,257 patients aged 18 to 65 who underwent bariatric surgery at Vanderbilt Health between 2017 and 2022. They also reviewed data from 1,809 patients treated with semaglutide or tirzepatide between 2018 and 2023. Patients with a history of end-stage renal disease or congestive heart failure were excluded from the analysis.
Body composition was measured using bioelectrical impedance analysis. This method estimates fat mass and fat-free mass based on factors such as height, weight, age, race, gender, diabetes history, and duration of GLP-1 treatment.
According to the researchers' findings over a period of 24 months: "both medical and surgical weight loss approaches led to significant reductions in FM (fat mass), modest reductions in FFM (fat-free mass), and increases in the FFM/FM ratio," indicating improved body composition. The study also noted that male patients experienced better long-term preservation of fat-free mass compared to female patients.
First authors Zicheng Wang, MS (graduate student), and Lei Wang, PhD (postdoctoral fellow), both from Epidemiology contributed to the paper. Additional co-authors included Xinmeng Zhang and You Chen, PhD (Biomedical Informatics and Computer Science); Brandon Lowery (Vanderbilt Institute for Clinical and Translational Research); Lauren Lee Shaffer, MS; Quinn Wells, MD (Cardiovascular Medicine); Charles Flynn, PhD; Brandon Williams, MD; Matthew Spann, MD; and Gitanjali Srivastava, MD (Surgery).
The research received partial funding through National Institutes of Health grants R01DK126721 and R01CA275864.
