GLP-1 agonists have been hailed as miracle drugs. Medications like semaglutide and tirzepatide are transforming the treatment of obesity, helping people lose weight when nothing else seemed to work. We have watched celebrities shed pounds…from Oprah Winfrey, Rosie O’Donnell and Serena Williams to Charles Barkley, Whoopi Goldberg and Elon Musk. We have written a lot about the pros and cons of GLP-1 weight loss drugs. Here is a new concern about the hidden cost of these “miracle shots”: slimmer bodies but weaker muscles.
Muscle Loss with GLP-1 Weight Loss Drugs
At the American College of Physicians Internal Medicine Meeting (ACP-IM) on April 17, 2026, researchers presented a sweeping review of 36 randomized clinical trials examining incretin-based therapies. We are talking about GLP-1 agonists like semaglutide (Ozempic, Wegovy) and liraglutide (Saxenda, Victoza) and the dual action GLP-1 and GIP receptor agonist (Mounjaro, Zepbound). These are some of the most sought after drugs in the US these days.
What they found was worrisome. In studies that measured body composition, the median proportion of weight loss coming from muscle-related tissue was about 35%. Even more concerning, over two-thirds of the trials exceeded accepted benchmarks for muscle loss.
What most people care about is the number on the scale. How many pounds have been shed. They love seeing the numbers come down. What they may not realize, though, is that GLP-1 weight loss drugs are stealing strength along with pounds.
It’s Not Just Fat That Is Disappearing
While it is absolutely true that many people can shed pounds while taking GLP-1 weight loss drugs, they may also lose lean body mass.
Remember that muscles are essential for:
- Strength
- Balance
- Metabolic resilience
- Independence with aging
The more dramatic the weight loss, the more muscle tends to disappear along with it. That’s not a by-the-way. That’s a worrisome biological tradeoff.
We Warned About Muscle Loss with GLP-1 Weight Loss Drugs Over 2 Years Ago:
To tell the absolute truth, it wasn’t us. It was a frequent guest on The People’s Pharmacy nationally syndicated radio show, Dr. Robert Lustig!
Robert Lustig, MD, MSL, author of Metabolical
Robert Lustig, MD, MSL, is Professor Emeritus of Pediatrics in the Division of Endocrinology at the University of California, San Francisco. He specializes in the field of neuroendocrinology, with an emphasis on the regulation of energy balance by the central nervous system. His research and clinical practice has focused on childhood obesity and diabetes.
Dr. Lustig alerted our listeners to the muscle loss problem and other side effects of GLP-1 weight loss drugs. He is a compelling speaker and a knowledgeable expert. Here is a link to Show 1362: Lowdown on New Medicines for Treating Obesity –Part 2. You can listen by clicking on the arrow inside the green circle below the woman on the scale. I believe you will find Dr. Lustig’s perspective of significant interest.
Is This a Drug Problem—or a Weight Loss Problem?
Here’s where things get a bit confusing. Even people losing weight through diet or placebo interventions also lost muscle. About half of those groups exceeded the same muscle-loss thresholds.
So the GLP-1 weight loss drugs and muscle loss signal may reflect a broader truth:
Weight loss itself can come at a muscular price.
But here’s the catch: these GLP-1 weight loss drugs drive more weight loss, and that may amplify the problem.
The Missing Piece: Does Muscle Loss Lead to Weakness?
You might have expected the researchers who studied GLP-1 drugs to measure whether people actually got weaker. They didn’t.
As far as we can tell, not a single trial assessed objective physical function: no grip strength, no walking speed, no real-world mobility.
That leaves a massive gap in our understanding of GIP and GLP-1 weight loss drugs.
We know that muscle is being lost. We do not know what that means for strength, stability and/or independence.
A Red Flag for GLP-1 Weight Loss Drugs and Older People
We are concerned about the use of these powerful weight loss drugs in older adults. Very few studies included older participants. None focused specifically on people over 65, the group most vulnerable to muscle loss.
For them, losing muscle isn’t cosmetic. It can mean:
- Falls
- Fractures
- Loss of independence
That makes the GLP-1 muscle loss signal more than academic. It could have real-world consequences!
An Early Warning About GLP-1 Weight Loss Drugs That Was Easy to Dismiss
Long before this analysis, concerns were already being raised.
During our 2023 People’s Pharmacy interview with Dr. Robert Lustig, he warned that these drugs may push the body into a starvation-like state, leading to loss of muscle as well as fat.
At the time, that warning competed with enormous enthusiasm for these medications. Now, the new GLP-1 muscle loss signal suggests he may have been onto something.
Can The Tradeoff Be Avoided?
Experts are not suggesting people abandon these medications. The benefits, especially for metabolic disease, are substantial. But they are urging a shift in mindset.
Weight loss alone is not enough. The real goal should be:
Lose fat. Preserve muscle. Maintain function.
That likely means combining medication with:
- Resistance training
- Adequate protein intake
- Monitoring strength, not just pounds
The Bottom Line:
GLP-1 Weight Loss Drugs Are a More Complicated Story
GLP-1 drugs are powerful. They do work for many people, though there are a number of serious side effects.
But the emerging GLP-1 muscle loss signal complicates the narrative. This isn’t just about getting thinner. It’s about what the body gives up in the process.
One question looms large:
Are we trading strength for slimness without realizing it?
We would love to hear from you. Have you taken any of the GLP-1 and/or GIP receptor agonist drugs such as Ozempic, Wegovy, Saxenda, Victoza, Mounjaro or Zepbound. Remember, some of these medications are also prescribed for type 2 diabetes. Did you experience benefits? Did you experience side effects? Please share your story in the comment section below. And if you know someone who has been taking one of these drugs, please share this story with them. They may not realize that strength training could be an essential component to taking GLP-1 weight loss drugs. Thank you for supporting our work.
