Let’s say you’ve decided it’s time to “get in shape.”
So you start doing cardio — running, biking, group fitness classes, or hitting the treadmill. You’re sweating more. You’re breathing harder. It feels like progress.
But after weeks of effort, your body isn’t toning up or adjusting the way you hoped. Maybe you’re losing weight, but still feel soft, tired, or stuck.
Here’s the truth most people don’t realize: cardio alone usually isn’t enough to build the body — or the health — you want.
Let’s walk through why that is, and what your body really needs to feel better, get stronger, and lose fat in a sustainable way.
Why Cardio is Necessary
Cardio is good for your body. There’s no question about that.
It strengthens your heart and lungs, it helps your blood flow better, and it can improve blood sugar control and give your brain a boost†. Many people also find that cardio helps them feel less stressed or anxious, thanks to the feel-good chemicals (endorphins) your brain releases when you move.
It also burns calories while you're doing it, which can help with fat loss if you’re eating well.
So cardio is not the problem. The problem is thinking cardio is all you need.
If all you’re doing is cardio, you’re missing a huge piece of the puzzle — your muscle.
Where Cardio Alone Usually Falls Short
Cardio has some great benefits, but it’s not a one-size-fits-all solution for getting in shape. One of the biggest things it doesn’t do well is build or maintain muscle. And muscle is what gives your body shape, tone, and long-term strength.
Even if you’re burning calories with cardio, it doesn’t do much to raise your resting metabolism — the amount of energy your body uses just to keep you alive. So while cardio burns calories in the moment, it doesn’t do much to help your body burn more calories all day long.
In fact, if you’re doing a lot of cardio and not eating enough, your body may actually start breaking down muscle for energy. That makes your metabolism slower over time, and can make weight loss harder later on.
People also often overestimate how many calories they’re burning through cardio. That can lead to frustration when the scale doesn’t move, or when progress stalls.
And even if you do lose weight with cardio alone, without strength training, you might still feel “soft” or weak — what many people refer to as “skinny-fat” — because your muscles aren’t being challenged or developed.
That’s where strength training comes in.
Muscle Is the Missing Link
Muscle is one of the most important — and overlooked — parts of any fat loss plan. That’s because muscle is metabolically active. It burns energy even when you’re not working out. So the more muscle you have, the more calories your body uses just to function each day.
When you lose fat but keep your muscle, your metabolism stays stronger. But if you lose muscle and fat, your body burns fewer calories — which can slow progress and make it easier to gain the weight back later.
Muscle also helps your body use insulin better†, keeps your joints healthier, and improves how well you move and feel. And if you want that toned look, you need muscle. More lean mass means a firmer, fitter appearance — even if the number on the scale stays the same.
So if you’re trying to lose weight, building or keeping muscle isn’t just helpful — it’s essential.
Why Strength Training Matters
Strength training is how you hold onto muscle while losing fat — and maybe even build more.
When you lift weights or use resistance bands, your muscles get a signal to grow or stay strong. This is especially important if you’re eating in a calorie deficit. Without that signal, your body may break down muscle for fuel. But with strength training, you tell your body that muscle is important and it needs to keep it.
It’s also how your body shapes up as you lose fat. Cardio may help with fat loss, but strength training helps you sculpt your frame and feel more confident in your skin.
And the benefits don’t stop there. Lifting weights supports stronger bones, better posture, healthier joints, and fewer injuries over time†. It also boosts your body’s ability to burn fat long-term.
And no — lifting weights won’t make you bulky. Getting bulky requires very specific and strict training and dieting for an extended period of time. You’re not gonna wake up one day and wonder how in the world you got so ripped after a little strength training.
What lifting weights will do is help you feel stronger, look more toned, and make everyday activities a lot easier.
What Really Works: A Balanced Approach
The best way to support your metabolism and long-term health is to combine three things:
-
Cardio to support heart health and boost energy.
-
Strength training to protect muscle and increase your resting metabolism.
-
Healthy nutrition with enough protein, calories, and nutrients to fuel your body and recovery.
When all three work together, you’re not just burning calories — you’re building a stronger, healthier body that can keep going for the long run.
If you’ve been doing cardio-only workouts and feeling stuck, you’re not alone. It’s one of the most common mistakes people make when trying to lose weight or “get fit.”
But now you know better.
Cardio has its place — it’s great for your heart and your brain. But if you want to change your body, improve your metabolism, and actually feel stronger, you need more.
You need muscle. And you need a plan that works with your body — not against it.
Strength training builds the foundation that cardio alone can’t. So the next time you head to the gym or press play on a workout video, don’t skip the strength work. Your future self will thank you.
If you’d like a specific plan to get you started with strength training, check out our blog post: What Happens When You Start Strength Training.
