Three reasons you’re losing centimetres but not weight

When you’re trying to lose weight, the number on your scale can feel like the most important metric on the planet. When it moves down you’re thrilled. If it gets stuck—or moves up a little—you may feel discouraged and think your healthy habits aren't working. But here’s the thing about losing weight: It almost never declines in a constant linear downward path.

It’s normal to have ups, downs, and plateaus. “Checking in on weight as a marker of progress can be a helpful tool for some, but it is by no means the be all and end all of health and fitness,” says Leah Barron, R.D., CPT, a registered dietitian and certified personal trainer in New York.

In fact, your weight can stay the same even if you’re seeing other positive signs, like your clothes fitting better. But as natural as it can be to lose centimetres and not weight, it can still cause distress. Something that can help: Understanding what’s going on and seeing that there’s more than one way to measure progress.

Here are three reasons your body might be getting smaller without losing weight (and what, if anything, you should do about it):

#1. You’re losing fat and gaining muscle

Exercise changes your body composition. Simply put, fat takes up more space than muscle but doesn’t necessarily weigh less. That net positive change shows up in the way your clothes fit.

While it can be a little discouraging to weigh the same thing you did when those pants felt tight, Barron says this indicates a change in your body composition. “This means that although your weight is staying the same, the percentage of fat tissue versus muscle tissue is changing—which is actually a much better indicator of health than weight alone.”

Body composition is what determines your total mass—it’s the sum total weight of the water, bone, muscle, organs, and fat that makes up your body. While your bone mass tends to stay pretty steady, the other factors can be fluid, changing both what you weigh and the size and shape of your body. Research has found that some unavoidable factors, like age, can alter your body composition over time, but others—like exercise—are under your control.

When you start exercising, especially if you’re weight training, you can lose fat and gain muscle. This may keep the scale steady (adding a kilo of muscle and losing a kilo of fat is a net zero equation) but it will help you lose centimetres. “Muscle tissue is denser than fat tissue, so it takes up less space,” says Barron. “This is exactly why your weight may not change, but your clothes are feeling looser.”

This is one of those situations where you should keep doing exactly what you’re doing. Don’t be tempted to stop weight training so that you don’t add muscle mass. This can backfire on you because when you lose lean muscle (which may happen when you lose weight), your metabolism can slow. “Your basal metabolic rate, or BMR, is generally the calories you're burning just existing—breathing and moving through your day doing the things you normally do,” says Audra Wilson, M.S., R.D., LDN, bariatric dietitian at the Northwestern Medicine Metabolic Health and Surgical Weight Loss Center, Illinois, United States. “However, when you lose mass, your BMR can go down a bit, too.”

The reasons for this are unclear, but studies have found that the body adapts to weight loss—and makes keeping the weight off that much harder—by slowing the metabolism. In other words, you ultimately burn fewer calories over the course of the day, which can set you back in your weight-loss goals over time. Building muscle, however, can offset this dip. “The muscle is going to burn more calories at rest than fat would,” Wilson says, ultimately helping you get over this plateau and continue to lose weight.

#2. Your body has adjusted to the new routine

If all of a sudden you’ve stopped losing weight even though you’re doing everything the same, it could be your body’s ability to adapt. “Over time, your body has what’s called compensatory measures, which are ways it adjusts to increased energy expenditure over time,” Wilson says. So, for example, when you first start lifting weights, you burn more calories and see a difference in your body and on the scale. Then, over time, your body adapts to the exercise as it works more efficiently. “Your cardiovascular system gets in better shape, basically,” says Wilson. “Your muscles work more efficiently, and you don't burn as many calories.” The result: You’re losing centimetres but not weight.

How to kickstart weight loss again?

We wish there was an easy answer but here are two tried and true ways that might get the scale moving:

First, check-in on your eating habits.

Sometimes as we progress on a weight loss journey, we let up on some of our diet goals. If your eating habits are the same, you might need to cut back on calories because the amount of calories your body needs throughout the day may have decreased with your prior weight loss.

Next, consider levelling up your exercise routine.

Baron says to take your current workout as your starting point, then add to the amount of weight you’re lifting—instead of three kilograms, try five. Or, increase the number of reps you’re completing. If you’re doing a cardio workout, pick up the pace or go for longer, like increasing from a brisk walk to a jog or adding another 5 minutes to your exercise time. If this seems like an impossible task, consider the confidence that comes with being able to lift heavier weights or feeling less out of breath.

#3. Your scale may need recalibrating

If you’re exercising and staying on track with your eating habits and losing centimetres but not weight, this may be an opportunity to check that your scale is calibrated properly, says Christi Smith, M.S., CSCS, a certified strength and conditioning specialist. Calibrating your scale is a way of restoring its accuracy, which is important if you moved it from a different room or if it’s not on a flat surface. (For calibration how-to’s, consult the scale manufacturer’s website.)

It’s also important to establish a consistent weight tracking routine. A good plan is to weigh yourself at the same time each day, Smith says. Try first thing in the morning after using the bathroom, since you won’t have meals, beverages, or clothes interfering with the number. And remember: Weighing yourself consistently over time gives you the big-picture scope of your progress and is better than judging it by any one day’s number.

Tracking progress without using the scale

Because the scale is just one way to evaluate improvement, it’s worth finding other non-scale victories to measure success and stay motivated. In fact, “weight is actually the least helpful measure of fitness and health,” says Barron. She recommends looking at more objective metrics, like blood pressure and blood sugar, which can be more accurate indicators of health over time. “Then, there are more subjective measures you can track on your own, like quality of sleep, energy levels, stress management, increases in strength and endurance in your workouts, and changes in mental health,” Barron says.

Another key measure is to notice changes in the amount of effort required for ordinary tasks like carrying groceries, or keeping up with friends on a hike. “Considering the ease with which you move through the world and the ability to do the things that you want to do without having to think twice is huge,” Wilson says. “Doing activities you enjoy without limitations is a much more positive goal than a singular number.”

The bottom line

The number on the scale isn’t the only measure of success. Losing centimetres counts, too. Stay inspired during times when the scale seems stuck by taking measurements of your body. Ultimately it’s the non-scale victories—like feeling better and having more energy—that are most impactful to your overall health and confidence.