Researchers at Vanderbilt Health discovered that both popular weight loss drugs and bariatric surgery significantly reduce fat mass while causing modest losses in fat-free mass, including muscle, in patients with obesity. The findings, based on over 3,000 patients, show improvements in overall body composition over 24 months. Maintaining this balance is crucial for long-term health, the study emphasizes.
A team led by Danxia Yu, an associate professor of medicine in epidemiology, and Jason Samuels, an assistant professor of surgery, analyzed electronic health records from Vanderbilt Health patients. The retrospective study included 1,257 individuals aged 18 to 65 who underwent bariatric surgery between 2017 and 2022, and 1,809 patients treated with semaglutide or tirzepatide from 2018 to 2023. Patients with end-stage renal disease or congestive heart failure were excluded, and body composition was assessed using bioelectrical impedance analysis, which estimates fat mass and fat-free mass based on factors like height, weight, age, race, gender, diabetes history, and treatment duration. The research was published in JAMA Network Open, with first authors Zicheng Wang and Lei Wang from epidemiology. Contributors included experts from biomedical informatics, cardiovascular medicine, and surgery, supported by National Institutes of Health grants. Over 24 months, both treatments produced substantial reductions in fat mass alongside smaller decreases in fat-free mass. This resulted in an increased ratio of fat-free mass to fat mass, indicating better body composition. Male patients preserved fat-free mass more effectively than females over the long term. Higher fat mass correlates with greater risks of death from obesity-related issues like cardiovascular problems, while more fat-free mass links to lower mortality risks. The researchers called for further studies on these shifts in real-world settings.
