When I started on tirzepatide, I cared about one number, and it was the one on my bathroom scale. I had carried an extra 30 pounds for over a decade, and I wanted every last one of them gone.

What I didn’t know, and what nobody told me, is that your scale can’t tell fat from muscle. When you lose weight, your body doesn’t only let go of the parts you want to lose. It can take some of your muscle with it.

That caught me off guard, and I’ve since learned it catches almost everyone off guard. Now that so many people are taking a GLP-1, I think it’s one of the most important things to understand before you start.

What happens when the weight comes off

In one large study of tirzepatide, the same medication I started on, about a quarter of the weight people lost was lean mass. Lean mass is everything in your body that isn’t fat, and muscle makes up a big part of it.

That isn’t a reason to be scared of these medications. People lose some muscle with almost any kind of weight loss, including plain old dieting. But it is a reason to pay attention, because muscle is what keeps you strong, steady on your feet, and able to do the things you love as the years go by.

Losing fat makes you lighter. Keeping your muscle is what helps you feel good in the body you end up with.

What my numbers looked like

Over nine and a half months, I lost 32 pounds. My body composition scans showed that 27 of those pounds were fat and 5 were muscle. At the six-month mark, I was down 16 pounds of fat and 3 of muscle.

I’ll admit those five pounds of muscle stung a little when I first saw them. But I also know that number could have been much bigger if I hadn’t been watching it, and that’s really the whole point of this post.

At 61, I wasn’t trying to get skinny. I wanted to feel strong again. My knee hurt less, I slept better, and I felt years younger, and none of that comes from losing muscle.

What I did to hold on to my muscle

Nothing I did was fancy, and none of it required a personal trainer or a perfect week. I made protein a priority at every meal, because your muscles need it most when you’re eating less overall. I kept up with strength training, even on days I didn’t feel like it. I paid close attention to what I ate, and I stayed active, which for me mostly meant walking.

I gave myself permission to think long term and imperfect. Some weeks I hit all of it and some weeks I didn’t, and my scans kept me honest either way.

Why your scale isn’t enough

Your bathroom scale tells you one thing, which is how much you weigh. It can’t tell you whether you lost three pounds of fat or three pounds of muscle, and those are two very different weeks.

Your scale won’t tell you that.

That’s why everyone who starts with us gets a body composition scan. A body composition scan shows how much of your weight is fat, how much is muscle, and which way each number is moving. If your muscle starts slipping, we see it early and change your plan before it becomes a problem.

What we do differently

A lot of people get their medication through an app now, and I understand why. It’s quick, and it feels simple. But an app can’t sit down with you, look at your scan, and tell you it’s time to add more protein or pick up some weights.

That’s my job, and it’s the part I love most. I coach every person I work with on keeping their muscle, and together we build a plan focused on holding on to as much of it as possible while you lose weight safely. You’ll see the same people every time, and we’ll know your name, your schedule, and your numbers.