A study has revealed that GLP-1 therapy, when paired with a balanced diet and regular exercise, can effectively reduce body fat while maintaining lean muscle mass.
The findings, presented at the European Congress on Obesity (ECO 2025), show that both GLP-1 monotherapy and dual GLP-1/GIP therapy can achieve fat loss without compromising muscle mass.
GLP-1 is a type of incretin, a gut hormone that regulates blood sugar levels, and GLP-1 receptor agonists are drugs that mimic or enhance the action of this natural hormone.
These medications work by stimulating insulin release after meals, reducing glucagon secretion, slowing stomach emptying, and increasing feelings of fullness to curb appetite.
GLP-1 receptor agonists such as semaglutide and liraglutide were developed to treat type 2 diabetes, but several studies have also confirmed their effectiveness in managing obesity and helping with weight loss.
With both GLP-1 and GIP receptor agonists approved for treating type 2 diabetes and obesity, there’s high demand for these therapies. Monitoring muscle mass and potential muscle loss in patients using these medications is crucial.
Although GLP-1 treatments have shown promising weight loss results, questions lingered about their impact on muscle preservation.
To address this, researchers conducted a six-month prospective cohort study involving 200 overweight or obese adults aged 18 to 65.
The study prescribed semaglutide (a GLP-1 medication) to 80 participants and tirzepatide (a dual GLP-1/GIP medication) to the remaining 120.
A specialist obesity physician guided all participants on the correct medication usage, resistance exercise method, and appropriate protein intake.
Body composition was measured using the InBody 570 at the start, midpoint, and end of the study, providing comprehensive data on water content, muscle mass, body fat percentage, and muscle distribution.
Researchers focused on changes in fat and muscle levels post-treatment and considered medication adherence and lifestyle habits.
The study group, with an average age of 47 and a median BMI of 31.4, saw significant weight reductions after six months of treatment.
Women lost an average of 19 pounds, dropping from 156 to 137 pounds, while men shed 30 pounds on average, going from 223 to 193 pounds. This represented a 13% weight loss for women and 12% for men.
Importantly, women lost an average of 23.8 pounds (10.8 kg) of fat while only losing 1.4 pounds (0.63 kg) of muscle. Men lost an average of 26.5 pounds (12 kg) of fat and just 2.2 pounds (1 kg) of muscle.
Medication adherence was high, at 95% for the first three months and 89% for the latter half of the study. Preliminary feedback suggests that consistent strength training and adequate protein intake were key factors in maintaining muscle mass and strength.
The ongoing study continues to collect data. While comparing the effects of tirzepatide and semaglutide, researchers found that both GLP-1 and dual GLP-1/GIP therapies effectively reduce weight and body fat.
They note that some muscle loss during weight reduction is normal, but following a regimen supervised by obesity specialists can minimize this loss. The team emphasizes the need for further research into how diet and exercise interact with these medications to preserve muscle mass during weight loss.
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