The study shows minimal muscle mass loss with GLP-1 and GLP-1/GIP therapy with weight loss

The study shows minimal muscle mass loss with GLP-1 and GLP-1/GIP therapy with weight loss

New research will be presented at this year's European Congress on Obesity (ECO 2025, Malaga, Spain, May 11-14) showing that patients receiving GLP-1 or combined GLP-1/GIP receptor agonist therapy with weight loss experienced minimal muscle mass loss based on weight loss over 6 months of treatment. The study comes from Dr. Dinabel Peralta-Reich, Donald and Barbara Zucker School of Medicine at Hofstra/Northwell; Lenox Hill Hospital, Northwell Health, New York City, NY, USA and Dr. Alexandra Filingeri, New York Weight Wellness Medicine, New York City, NY, USA and colleagues.

GLP-1 (glucagon-like peptide-1) receptor agonists, which include semaglutide and liraglutide and were originally used for type 2 diabetes, have also been shown to be effective in treating obesity and promoting weight loss. More recently, tirzepatide, which combines GLP-1 and GIP (glucose-dependent insulinotropic polypeptide), has also been approved for the treatment of type 2 diabetes and/or obesity. As research continues to support the use of these medications, monitoring body composition, particularly muscle mass and atrophy, remains clinically significant. Obesity medicine specialists play a key role in designing interventions that promote weight loss while maintaining lean mass.

In this six-month prospective cohort study, 200 adults (18-65 years, BMI 25 kg/m² or more, with overweight or obesity) were prescribed GLP-1 receptor semaglutide or GIP-1/GIP dual agonist tirzepatide (60% of participants received) (N=80). Semaglutide. Participants received education on medication use, resistance training, and protein intake from a board-certified obesity physician.

Body composition was measured at baseline, three months and six months using bioelectrical impedance using a system referred to as the Inkodas 570. The Inbody 570 is a professional body composition analyzer that provides a detailed breakdown of muscle, fat and water distribution using multi-frequency bioelective impedance analysis (BIA). It measures total body water (intracellular/extracellular), skeletal muscle mass, body fat percentage, visceral fat and segmental muscle distribution.

Primary outcomes included changes in body fat and muscle mass, with data analyzed using statistical modeling. Qualitative data on medication adherence, physical activity, and diet were also collected. Participants served as self-controls for pre- and post-intervention comparisons.

All 200 participants (99 men, 101 women) completed the study. The average age was 47 years with an average baseline BMI of 31.4 kg/m² (but all over 25, all living with overweight or obesity). After six months, the women's average weight fell from 156 pounds (71 kg) to 137 pounds (62 kg) - a loss of 12%; While the average weight of men fell from 223 pounds (101 kg) to 193 pounds (88 kg) - a loss of 13%.

After six months, women had lost an average of 10.8 pounds of fat mass but only 1.4 pounds of muscle mass (0.63 kg), while men had lost 25 pounds of fat mass (12 kg) and only 2.4 pounds of muscle mass (1 kg).

Medication adherence was 95% at three months and 89% at six months based on self-reports. Qualitative data showed that regular resistance training and consistent protein intake were associated with better muscle retention and strength. The study remains ongoing and more data continues to be collected. The differences between weight/lean mass/fat mass for tirzepatide and semaglutide are still being analyzed.

The authors say: “This six-month study shows that GLP-1 and dual GLP-1/GIP receptor agonists are effective in reducing weight and body fat mass in individuals with obesity. While some muscle loss is expected, the study suggests that with close supervision from an expert obesity doctor, muscle loss can be minimized. Factors such as self-reported protein intake, medication adherence, and regular follow-up contributed to success. Data shows that these drugs help people lose body fat while maintaining lean mass. Further research is needed to better understand the role of diet and exercise in maintaining muscle mass. “

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