Preserving Muscle During GLP-1 Weight Loss

Blockbuster GLP-1 receptor agonists revolutionized obesity management in recent years, driving weight loss of up to 20%.

This weight loss, however, can carry a notable downside: Studies estimate that 15% to 40% of GLP-1-induced weight loss may come from lean body mass, not stored body fat.

“GLP-1 medications are incredible and life-changing weight-loss drugs. They are overall safe and effective medications, but my greatest concern is muscle loss that can occur in patients using these medications,” Samantha Flanagan, DO, of Temple Health in Philadelphia, told MedPage Today.

Weight loss inherently risks muscle depletion, and mitigating that loss is key, added Allison Rhodes, MD, of the Ohio State University Wexner Medical Center in Columbus. “Our goal is to maximize fat loss while preserving as much muscle as possible,” she said.

Tracking Body Composition

To evaluate body composition changes over time, clinics are turning to bioelectrical impedance analysis and, occasionally, at-home bioimpedance scales.

These scales use low-level electrical current to measure fat mass, skeletal muscle mass, total body water, and visceral fat. This helps clinicians assess the quality, not just the quantity, of a patient’s weight loss, Rhodes told MedPage Today.

Scan frequency varies by clinical need. For patients actively pursuing weight loss or body recomposition, scans may occur monthly. For those in a maintenance phase, assessments may happen every 4 to 6 months.

“I often tell patients that the goal is not simply to lose weight; it is to improve body composition, metabolic health, strength, and long-term function,” Rhodes emphasized. “Body composition analysis helps us ensure that we’re achieving those goals in the healthiest way possible.”

The scans can help identify excessive lean mass loss early, Flanagan added, allowing clinicians to intervene quickly.

Staving Off Muscle Loss

Guarding against muscle loss often requires a multifactorial strategy centered on optimized nutrition and targeted exercise. Last year, four medical organizations jointly released a clinical advisory detailing nutritional priorities for patients treated with GLP-1 agents, noting that a daily protein target of 1.2 to 1.6 g/kg of body weight has been proposed during active weight loss.

A recent observational study reinforced this approach. Researchers found that 47.5% of weight lost by adults taking semaglutide (Wegovy) was lean mass, compared with 35.7% for those on diet and lifestyle interventions alone, when measured by dual-energy X-ray absorptiometry scans. However, semaglutide users with higher daily protein intake experienced significantly less lean mass loss in the study, even after adjusting for total weight lost.

“Managing to eat this much food can be difficult while on a medication like a GLP-1 drug, which suppresses appetite,” Flanagan pointed out. “I typically recommend eating protein first in meals to be sure you finish the protein portion of a meal, followed by veggies, then starches last.”

Rhodes also emphasized the importance of protein distribution throughout the day. “Spacing protein across meals and snacks helps provide a more consistent stimulus for muscle protein synthesis and may be particularly important during active weight loss,” she explained, recommending a high-quality protein source within a few hours of resistance exercise.

Resistance training is a “non-negotiable,” added Rhodes. “My minimum recommendation is two dedicated resistance-training sessions per week, with a goal of progressing toward at least 90 minutes of resistance training weekly using a progressive overload approach,” she stated.

“Research consistently demonstrates that resistance exercise is one of the most effective tools for preserving muscle mass and strength during weight loss,” she said.

Preserving muscle is particularly critical for adults over age 65, postmenopausal women, sedentary individuals, and those with a history of weight cycling. “Muscle can be difficult to rebuild once lost,” Rhodes stressed. “Taking a more measured approach can sometimes yield a better long-term outcome, even if weight loss occurs a bit more slowly.”

Dose Adjustments, Future Strategies

When dietary and exercise interventions fall short, clinicians may need to modify GLP-1 drug regimens by lowering the dose or temporarily pausing treatment.

“If a patient is already making a strong effort with nutrition and exercise and continues to lose muscle at an undesirable rate, I will absolutely discuss a temporary reduction in dose escalation — or in some cases a brief dose reduction — to allow time for the body to better preserve lean mass,” said Rhodes.

“Patients do not always love hearing that recommendation because they are understandably excited about seeing the scale move. However, I remind them that my goal is not simply to make them lighter; it is to help them become as healthy, strong, and functional as possible,” she added.

Flanagan agreed that dose escalation should be avoided if nutritional goals are compromised. “If someone can’t eat enough of the nutrition that their body needs, we always pause or sometimes de-escalate doses,” she said.

New therapies aim to eliminate this tradeoff entirely. For example, in a recent phase II trial, a combination of semaglutide with bimagrumab — an investigational activin type II receptor antibody intended to promote muscle growth — augmented fat loss while preserving lean muscle mass.