A recent study conducted by Vanderbilt Health researchers found that both bariatric surgery and certain weight loss medications (GLP-1 receptor agonists) contribute to improved body composition in patients with obesity. The research indicated that these treatments lead to a substantial reduction in fat mass (FM) accompanied by a moderate reduction in fat-free mass (FFM), which includes lean muscle. This alteration results in an increased ratio of fat-free mass to fat mass.
Study Findings
The study determined that both medical and surgical weight loss interventions demonstrated significant reductions in fat mass and modest reductions in fat-free mass. This led to an increase in the fat-free mass (FFM) to fat mass (FM) ratio, indicating an overall improvement in body composition. A higher percentage of fat mass is associated with an elevated risk of mortality from obesity-related diseases, while a higher percentage of fat-free mass is associated with protective benefits against mortality.
Research Methodology
The retrospective cohort study analyzed electronic health records from two patient groups at Vanderbilt Health:
- Bariatric Surgery Group: 1,257 patients (ages 18 to 65) who underwent surgery between 2017 and 2022.
- Medication Group: 1,809 patients treated with semaglutide or tirzepatide from 2018 to 2023.
Patients with a history of end-stage renal disease or congestive heart failure were excluded from the study. Body composition was assessed using bioelectrical impedance analysis, which provides estimates of fat mass and fat-free mass. Observations were recorded over a 24-month period.
Key Observations
- Both bariatric surgery and treatments with semaglutide or tirzepatide were associated with significant reductions in fat mass.
- Moderate losses of fat-free mass were observed in both treatment groups.
- An improvement in the ratio of fat-free mass to fat mass was noted across both intervention types.
- Male patients exhibited better long-term preservation of fat-free mass compared to female patients.
Context and Future Research
The findings contribute data regarding changes in body composition following these interventions. Researchers noted the need for further studies to observe these changes in real-world clinical settings.
Publication and Support
The findings were reported on January 9 in the journal JAMA Network Open. The study was led by Danxia Yu, PhD, Associate Professor of Medicine, and Jason Samuels, MD, Assistant Professor of Surgery. First authors of the paper were Zicheng Wang, MS, and Lei Wang, PhD. The study received support in part from National Institutes of Health grants R01DK126721 and R01CA275864.