GLP-1s and Muscle Loss: What the Evidence Actually Shows

[desinr-gal]

I think the answer is obvious. Muscles build in response to use, resistance and need. Strength training i.e. lifting weights builds muscles, atrophy occurs when lower/no resistance occurs.

Having loss over 50 lbs, I lost a Lot of muscle, because I have Not been lifting and carrying around those 50 lbs all day everyday. I started out working on lifting, but got sidetracked and then lazy.. Now I am much lighter and much weaker. and that makes perfect sense.

I can't even imagine what it would be like spending everyday navigating life with a 52lb weight on my back, and yet that was the life I was leading. I am much happier without it!

 

[woundcarping]

Awesome progress and numbers!

Thanks!

I think your point is key, and it raises an important question: what is actually being measured?

I didn't mean to make a particular point. The hinkiness in my data is with a couple numbers changing from the day of report (1/30) vs the comparison report made on 4/30. I corrected the data to the most logically rational results, but I'd like to harass them a bit since I've paid $600 for the data so far.

DEXA measures fat, bone mineral content (BMC), and "everything else" (lean mass). That "everything else" is volatile, primarily to fluid shifts but also food weight. For example, drinking a .5L bottle of water before scanning will make your lean mass increase ~1lb. Stomach contents (food) will show up as lean mass as well. Lean mass≠muscle fiber. Some advanced DEXAs can give a value for dry lean mass, or lean mass minus water mass.

...Pre-carbs = depleted muscle. Post-carbs = full muscle. DEXA would register that as a 10 lb muscle gain — but it’s clearly not new muscle fiber.

Probably hyperbole, but 10lb of weight gain from carbs would take 1000-1500g or 4000-6000 calories of carbs to accomplish. DEXA would show that as +10lb of lean mass, it does not show muscle fiber explicitly.

...Under the right conditions, small increases are even possible with a well-designed program...

I posit that for the average person cutting significant weight, the effort spent gaining that theoretically possible very small increase of muscle fiber would be better spent preserving their lean mass, cutting weight, and enjoying life. Once the weight is cut it is far easier and more practical to have meaningful fiber gains while at maintenance or preferably a surplus of calories.

I think quality of life and 2 year recomposition outlook significantly favors separating the cutting/maintaining from a protracted conservative cut + an effort to gain. I admit I have not specifically researched the time efficiency aspect.

Bottom line: We should worry a lot less about muscle loss on GLPs, as long as strength stays consistent.

Speed of weight loss, resistance training, and protein intake matters. Turning a blind eye to any of that is a great way to be disappointed with the outcome. I wanted scans as my typical weights I'm lifting aren't in the gym and noticing at work that I'm weaker would be harder to adjust for. Noticeable strength loss would be a lagging indicator for me beyond what I find acceptable.

Between my second and third scans I didn't go to the gym, didn't track macros, etc... mostly because I was being lazy, partly because I wanted to see what would happen between scans (which is why I took the third scan a month before I originally planned). It's no surprise I lost a higher percentage of lean mass during that period... but the loss was acceptable to me and significantly better than the Quarter Rule.

Loss speed and supplements can help with catabolism and be lean sparing, which I think my data illustrates.

I specifically target 1-1.1% weight loss per week... slower is more conservative than I want, while faster is more likely to be detrimental to my lean mass without additional efforts. If I'm losing 92/8 fat to lean, that implies I've been running a ~1260 calorie daily deficit for 21 weeks and counting.

I take consistently (doses have changed) took/take:

4mg HMB-FA daily (split 2x or 3x)

180mg Test C weekly (split 3x)

16mg Reta weekly (split 2x)

Since the 3rd scan I have added creatine. I'm loading at around 20g/day for ~10 days and will transition to 10g/day for the duration.

Holy moly this turned into a half/half length post!

 

[CharlieBrown]

Awesome progress and numbers!

I think your point is key, and it raises an important question: what is actually being measured?

DEXA scans measure muscle, fat, and bone — and that’s what most studies rely on. But DEXA can’t distinguish between fully hydrated muscles (loaded with water and glycogen) and depleted muscles. It sees both as the same lean mass. So you are required to control for consistency each time you measure (as you pointed out)

Everyone knows you can’t gain 10 lbs of true muscle in a weekend. Yet anyone who’s done keto and then eaten carbs for a few days has likely seen significant weight gain as a result. Pre-carbs = depleted muscle. Post-carbs = full muscle. DEXA would register that as a 10 lb muscle gain — but it’s clearly not new muscle fiber.

This same limitation applies to GLP analysis. When studies postulate fat and muscle loss on GLPs, a lot of nuance gets lost and compressed into a handful of broad categories.

For me, this reinforces the need for healthy skepticism — and a more practical framework: if weight loss is not accompanied by strength loss, there’s a good chance muscle fiber is being maintained. Under the right conditions, small increases are even possible with a well-designed program.

Bottom line: We should worry a lot less about muscle loss on GLPs, as long as strength stays consistent.

I'm sorry, but I have to disagree a little bit. Especially because some people will loose a lot of weight and be happy without realizing they lost a lot of muscle mass in the process.

Muscle Mass: Maintaining a healthy level of muscle mass is crucial for your overall health, healthspan, and quality of life. From metabolic benefits to injury prevention to support for cognitive function, muscle plays a fundamental role in all of these important areas.

One of the primary reasons muscle mass matters is its role in metabolism. Muscle is metabolically active tissue, meaning it requires energy (calories) to maintain. The more muscle mass you have, the higher your resting metabolic rate (RMR), which is the number of calories your body burns at rest. As you age, you naturally experience a decline in muscle mass, a condition known as sarcopenia. This leads to a slower metabolism.

I could go on and on.......

You don't have to do what I did; that's my choice. But you should have resistance training when using GLP's, esp. if you're over 50.

 

[CharlieBrown]

It's hard and unlikely to add a meaningful amount of muscle fiber while aggressively cutting weight, it's much more practical to add fiber while bulking.

With the assumption that the average person that came here was looking to lose considerable weight, the more practical goal seems to be preservation of lean mass/muscle fiber rather than trying to actually build muscle.

I've thought about making a thread about my data along the way, but let's put some of it in the post.

In the first 4-6 weeks of starting a GLP you'll shed the easy "water weight", the glycogen depletion and water, inflammation reduction, sodium/water normalizing, blood plasma volume normalizing.

Due to scheduling dumbness, I didn't get my starting weight Dexa near 12/12/25, my first Dexa was 7 weeks in to my GLP journey... there's some hinkiness with the data, which I'll bring up on my scan later this month and see if I can improve my confidence in the accuracy of the numbers below.

Dexa Data:

Metric 01/30/2026 03/25/2026 04/30/2026 Total Change (1→3) Total Weight 257.45 lb 238.77 lb 228.49 lb -28.96 lb Fat Mass 103.52 lb 77.26 lb 68.48 lb -35.04 lb Lean+BMC 162.61 lb (corrected) 161.50 lb 160.01 lb -2.60 lb Body Fat % 40.2% 32.4% 30.0% -10.2 points

So from 1/30 to 4/30, using Dexa data I lost 92% fat and 8% lean mass, with some margin of error.

Hydration is the biggest user controlled variable for body comp scans, I try to hydrate the same every time (and fasted) to reduce that particular variable. I started creatine after the 3rd scan so I'd have a baseline to compare the creatine increase in lean mass.

AI is pretty content that my actual muscle fiber atrophy is fairly low, in the range of ~1lb, with a "large" band of uncertainty (+/- ~1lb) because of scan repeatability, hydration changes, and other variables.

You're in the 1%.

That is fantastic !!

 

[Cannonball72]

Probably hyperbole, but 10lb of weight gain from carbs would take 1000-1500g or 4000-6000 calories of carbs to accomplish. DEXA would show that as +10lb of lean mass, it does not show muscle fiber explicitly.

Read correctly, exaggerated for the sake of the point.

Muscles will be empty of glycogen and water after keto, carbs will refill/replenish.

Body builders have been using this approach for decades. “Better than Steroids” has a whole chapter explaining the science. Fascinating to me.

 

[Cannonball72]

I'm sorry, but I have to disagree a little bit. Especially because some people will loose a lot of weight and be happy without realizing they lost a lot of muscle mass in the process.

Muscle Mass: Maintaining a healthy level of muscle mass is crucial for your overall health, healthspan, and quality of life. From metabolic benefits to injury prevention to support for cognitive function, muscle plays a fundamental role in all of these important areas.

One of the primary reasons muscle mass matters is its role in metabolism. Muscle is metabolically active tissue, meaning it requires energy (calories) to maintain. The more muscle mass you have, the higher your resting metabolic rate (RMR), which is the number of calories your body burns at rest. As you age, you naturally experience a decline in muscle mass, a condition known as sarcopenia. This leads to a slower metabolism.

I could go on and on.......

You don't have to do what I did; that's my choice. But you should have resistance training when using GLP's, esp. if you're over 50.

Disagreement is cool, no apologies needed (joke) The intent of the post was to get some dialogue about real experience going. Then pair it up and share the inadequacies of pure science, which is frequently less than perfect, especially in this realm. But that’s the beauty, its directional and we learn from it to improve our trajectories.

 

[CNCCurrency]

I’m not asking you to apologize, but no one appointed you as chief human content creation manager either.

Your view of appropriate vs inappropriate is yours. You don’t speak for everyone.

The value of the article is substantial. A summary is a useful way to get key points.

 

[CharlieBrown]

Disagreement is cool, no apologies needed (joke) The intent of the post was to get some dialogue about real experience going. Then pair it up and share the inadequacies of pure science, which is frequently less than perfect, especially in this realm. But that’s the beauty, its directional and we learn from it to improve our trajectories.

Sorry, I'm Canadian. There we again.......

And no, I don't know, "Office Glen". And if you're too young and have no idea what I'm talking about...

View: https://www.youtube.com/watch?v=sGkX1u-pG3s

 

[Smiter]

The F is goin' on here? GLPs cause weight loss.. Excessive weight loss, unrestrained by gear & co., will cause muscle mass loss. It's biology 102. What's the issue?

 

[CharlieBrown]

Sorry, I'm Canadian. There we again.......

And no, I don't know, "Office Glen". And if you're too young and have no idea what I'm talking about...

View: https://www.youtube.com/watch?v=sGkX1u-pG3s

Okay, just one more.....

View: https://www.youtube.com/watch?v=TL01SReeOqE

 

[CharlieBrown]

The F is goin' on here? GLPs cause weight loss.. Excessive weight loss, unrestrained by gear & co., will cause muscle mass loss. It's biology 102. What's the issue?

I dropped under 140lbs this morning..........139.8lbs

I'm going to have to buy pants in the kids dept. soon

 

[Smiter]

I dropped under 140lbs this morning..........139.8lbs

I'm going to have to buy pants in the kids dept. soon

140lbs???? That's half my ass.. What on earth are you looking to? Heartless, hair-less, fat less, man I know the divorce did you dirty and all, but you gotta rein it in, lest you end up nut-less. What're you, 5 feet?

 

[Smiter]

I dropped under 140lbs this morning..........139.8lbs

I'm going to have to buy pants in the kids dept. soon

I just realized...you're Bruce Lee weight...damn man. I used to biceps curl that weight for warm-up sets

 

[Cannonball72]

I just realized...you're Bruce Lee weight...damn man. I used to biceps curl that weight for warm-up sets

Last time I weighed 140 I was 8 years old - it’s only funny cuz it’s true

 

[Smiter]

Last time I weighed 140 I was 8 years old - it’s only funny cuz it’s true

I don't think I was even born that light. Ripped White Winkle must be doing it for a dare or something. Dude, @CharlieBrown , if you wanna get a new lady, you gotta be visible first... At 140lbs, you won't even have a shadow.

 

[mybodyisasewer]

I can't even imagine what it would be like spending everyday navigating life with a 52lb weight on my back, and yet that was the life I was leading. I am much happier without it!

All I'm hearing is that you should get into hiking since you're already conditioned for it.

 

[CharlieBrown]

140lbs???? That's half my ass.. What on earth are you looking to? Heartless, hair-less, fat less, man I know the divorce did you dirty and all, but you gotta rein it in, lest you end up nut-less. What're you, 5 feet?

I am 5'6"

 

[Smiter]

I am 5'6"

okay that alleviates some concern but 140lbs...there must be some law that forbids men from weighing that low. I know it's canada, but still..

 

[Grogu]

There should be a rule prohibiting this kind of thing.

Not that I want to be "that person", but there is a rule for that....



A frequent poster on here will occassionally post AI generated analyses which are extremely helpful, but there is always a disclaimer prior to the content saying something like, "generated by Gemini" or something to that effect. One telltale sign that something is AI generate are the long hypens. ChatGpt loves adding those for some reason.

I'm not sure of the intent of the original rule, but posting something as if you wrote it yourself is somewhat disingenous. The analysis itself is fine, all that was needed is a little disclosure. Like, "I asked ChatGPT to analyze the article and here's what it said."

Another problem is that analyses by AI are subject to bias and are not always correct.... but that's an entirely different topic.

 

[Grogu]

The F is goin' on here? GLPs cause weight loss.. Excessive weight loss, unrestrained by gear & co., will cause muscle mass loss. It's biology 102. What's the issue?

Yeah, this is what I was thinking. The real question (and I haven't had a chance to look at the articles yet) is if glp-1s cause more muscle loss than the equivalent amount of weight lost the "old" way through diet and exercise.

I've lost 115 pounds off my body so far. That's literally like carrying around a small person on my back 24/7. Was some of that muscle? I'm sure. But that's my body's adapting. I don't need as much muscle since I'm not carrying that 115 person on my back anymore.

I'm not negating the benefits of resistance and wish I had done more in my journey. But losing some muscle is the body's nature adaption to needing less. I'm not convinced that glp-1s make you lose more muscle than you would otherwise at an equivalent weight loss.

To me this is kind of like hair loss. Do people on glp-1 experience hair loss. YES, some do. But is that related to the glp-1 medications or rapid weight loss with not enough protein or the medications?