What GLP-1s Do to Your Muscle — and Why Lifting Matters More, Not Less

Earlier this week I wrote about where the gym fits when you’re on a GLP-1 — if you missed it, that one’s worth reading first. This picks up right where it left off.

Here’s the part nobody warns you about enough: when you lose weight on a GLP-1, you don’t only lose fat. You lose muscle too, sometimes a lot of it.

Research on these medications has found that a meaningful share of the total weight lost, sometimes a third or more, can be lean muscle mass rather than fat.

That’s not a scare tactic.

It’s just what happens when your body is losing weight quickly and isn’t given a reason to hold onto the muscle it has.

And muscle isn’t just about how you look. It’s your metabolism.

It’s your strength to carry groceries, get up off the floor, keep up with your kids or your grandkids. I hear often from those NOT strength training about how things are getting harder to do around the house (like carrying laundry up or down the stairs).

It’s a big part of why weight tends to creep back for people who lose it and then stop paying attention to this piece — less muscle means a slower metabolism, which means it’s easier to regain the weight once the medication or the routine changes.

Read that again.

Less muscle means a slower metabolism, which means it’s easier to regain the weight once the medication or the routine changes.

So if muscle loss is the real risk, cardio isn’t the answer.

Cardio’s great for your heart and it’ll burn calories, but it doesn’t tell your body “keep this muscle around.”

Only one thing does that: making your muscles work against real resistance, consistently, over time.

This is important: Your body holds onto what it’s using.

Again, re-read what I just shared: cardio isn’t the answer.

That’s why lifting matters more right now, not less.

Not because you need to be doing more, or pushing harder than you’re ready for — but because strength training is the one piece of this that actually protects the muscle you have while the medication does its part on the appetite and metabolism side.

To be clear: I’m not a doctor, and this isn’t medical advice — talk to whoever’s managing your prescription about what’s right for you.

But from where I sit as a coach, this is the piece that gets left out of the conversation most, and it’s the one we can actually help with.

Doctor’s or prescribers will often say “make sure you are working out.” I’m here to say “make sure you are strength training and lifting weights (heavy weights relative to you)”

Next up: how we actually build a program around this — what a week looks like, how hard is too hard, and how we adjust as you go.

-Coach Amanda