GLP-1 Study: Same Weight Lost, Very Different Strength
A new study in Nature Medicine is getting a lot of attention this week, and I think it's one of the most useful GLP-1 headlines so far. Researchers in Australia followed 120 adults on tirzepatide (the medication sold as Mounjaro) for 40 weeks. Half of them also lifted weights three times a week. Both groups lost almost the same amount of weight. The difference showed up in what that weight was made of, and in how strong people were at the end.
Even if you've never touched a GLP-1, this study has something to teach you about the scale.
What the study actually found
The trial is called T-REx. The people in it were men and postmenopausal women, ages 50 to 70, without diabetes, with overweight or obesity, and they were prescribed tirzepatide by the research team. Half were randomly assigned to supervised one-hour strength sessions three times a week, and they showed up to 91% of them. The other half kept doing their usual activities. Everyone got general advice on water, protein and fiber.
Here's what the researchers reported after 40 weeks:
Both groups lost about 49 pounds, and the difference between them was not meaningful.
Fat loss was also about the same in both groups.
The lifting group lost about 25% less lean tissue, which includes muscle.
Upper and lower body strength went up about 10% in the lifting group and went down about 10% in the group that didn't lift.
So two people could step on the scale and see the same number, and one of them got stronger while the other got weaker.
What the headline leaves out
A few honest notes. The people in this study were 50 to 70, so we don't know exactly how this plays out for a 35-year-old. The lifting was supervised in a research gym, which is a lot more structure than most of us have on a Tuesday night. The study measured body composition with a DXA scan, not a bathroom scale. And the drug maker supplied the medication for free. The paper's funding section says the company provided no other funding and had no role in running the study.
Also, this isn't a reason to start or stop any medication. That's a conversation for you and your doctor. My honest take is that the medicine is a tailwind, not the map. It can make the trip easier, but it doesn't tell you where to go or how to build the body you want to live in.
What it means for you
Here's the part I want you to sit with. The scale weighs the whole building: fat, muscle, water, food in your gut, all of it. This study shows two groups with the same number on the scale and very different bodies underneath.
That's exactly what we see with people who already work out and feel stuck. They're doing the workouts, but stress is high, sleep is short, meals are random, and it can feel like your body is holding on. The scale doesn't move much, so they decide nothing is working. Often more is changing than the scale can show.
Muscle doesn't live on its own, either. In our experience, it also needs real food, enough sleep, and less day-to-day stress. This study tested the lifting. Food, sleep and lower stress are what we use to support that work.
Game plan
Track one strength number, not only your weight. Pick one lift, like a squat or a row, and write it down every week. If it's going up, your body is changing in a good direction.
Lift two or three times a week. The study used three sessions, but in our experience a consistent two beats an ambitious four you can't keep up.
Eat real food often enough to recover. Protein, vegetables, fruit and water through the day give muscle what it needs.
Protect your sleep. Recovery happens at night, and short sleep makes everything harder, including workouts.
FAQ
I'm on a GLP-1. Should I start lifting? Talk to your doctor first, especially if you're new to exercise. This study suggests strength training alongside the medication helped people keep more muscle and get stronger, and a good coach can help you start at the right level.
I'm not on any medication. Does this apply to me? Yes. Losing some lean tissue happens with weight loss by any method, according to the lead researcher. Strength work, real food and sleep help you hold on to more of it.
Why isn't the scale moving when I work out? The scale can't tell muscle, fat and water apart. Track strength, energy and how your clothes fit alongside your weight.
The system matters more than the workout
Workouts are the easy part to plan. The hard part is putting food, sleep, stress and movement together and sticking with it when life gets busy. That's what the 8-Week Program is built for, with real accountability every week, so you're not guessing alone. We do this because we love our bodies, not because we hate our bodies.
If you want a quieter week to try the food, water and sleep pieces first, the $27 7-Day Reset is a simple place to start.
Want to talk about where you're stuck? Book a free 15-minute call.
If this helped, share it with a friend who's been staring at the scale.
