Why Cardio Alone Won't Get You the Results You Want

If you've been doing cardio consistently and your body still isn't changing, you're not alone — and it's not your fault. Cardio is great for your heart, your mood, and your overall health, but on its own it's one of the least effective tools for changing how your body looks. The real key to lasting fat loss for women is strength training combined with the right nutrition. Here's why — and what I recommend instead.

Cardio burns calories while you're doing it — that part is true. A 30-minute run might burn around 250–350 calories depending on your pace and body weight. But here's the problem: as soon as you stop, the calorie burn stops too. And over time, your body adapts.

Research published in Current Biology found that the relationship between physical activity and energy expenditure plateaus at higher activity levels — a concept known as constrained energy expenditure. In simple terms, when you do more cardio, your body compensates by reducing energy output elsewhere. You burn less during the rest of your day without even realising it.

This is why so many women tell me they're "doing everything right" — running three or four times a week, maybe hitting a spin class — but their body looks the same as it did six months ago. The effort is real. The approach just isn't working the way they think it is.

I see this pattern constantly with new clients here in Perth — women juggling work, kids, and 40-degree summers, doing their best with whatever time they have. They come to me frustrated after months of cardio-focused training and they're confused about why nothing has changed. The answer is almost always the same: they're burning calories, but they're not building the thing that actually changes body composition — muscle.

When you eat in a calorie deficit — which is necessary for weight loss — your body needs to get energy from somewhere. If the only signal you're giving your body is cardio, there's no strong reason for it to hold on to muscle. So it doesn't.

A study published in the American Journal of Clinical Nutrition by Bryner et al. found that participants on a calorie-restricted diet who only did cardio lost significant amounts of lean muscle mass alongside fat. In contrast, participants who did resistance training in the same deficit preserved their muscle almost entirely.

This matters more than most people realise. When you lose muscle, your resting metabolic rate drops — meaning you burn fewer calories just existing. This is how people end up in a cycle where they're eating less, exercising more, and still not losing weight. Their metabolism has slowed down because they've lost the muscle that was keeping it running.

A 2020 systematic review in Sports Medicine confirmed that resistance exercise is significantly more effective at maintaining or increasing resting metabolic rate compared to aerobic exercise alone. In practical terms, every kilogram of muscle you carry burns roughly 12–13 calories per day at rest, compared to about 4–5 calories per kilogram of fat. That difference compounds over time.

Strength training does three things that cardio alone cannot.

First, it preserves muscle while you're in a calorie deficit. As I mentioned, this keeps your metabolism from slowing down — which is the number one reason diets fail over time.

Second, it creates what's called excess post-exercise oxygen consumption (EPOC). After a strength session, your body continues to burn calories at an elevated rate for up to 24–48 hours as it repairs muscle tissue. A cardio session burns calories during the workout and then returns to baseline almost immediately.

Third — and this is the one I care about most as a coach — strength training changes your body composition. Two women can weigh the same on the scale, but the one who strength trains will look completely different. She'll have visible muscle tone, a tighter waist, and a more defined shape. That's not about the number on the scale. It's about what your body is made of.

A 2015 study published in Obesity followed women over a 12-month period and found that those who combined resistance training with a calorie-controlled diet lost more body fat and retained more lean muscle than those who did diet and cardio alone — even when total weight loss was similar between groups.

When it comes to burning calories during a workout, cardio wins — a 30-minute run can burn 250–400 calories compared to 150–250 for a strength session of the same length. But that's where cardio's advantage ends.

After a cardio session, your calorie burn returns to baseline almost immediately. After a strength session, your body continues burning calories at an elevated rate for up to 24–48 hours while it repairs muscle tissue. This is called excess post-exercise oxygen consumption, or EPOC — and over the course of a week, it adds up to significantly more total energy burned.

The biggest difference is what happens to your body composition. Cardio in a calorie deficit often leads to muscle loss alongside fat loss — which is why so many women lose weight but still don't look or feel the way they expected. Strength training in the same deficit preserves your muscle, which keeps your metabolism healthy and gives your body visible shape and definition as the fat comes off.

Long term, cardio-only approaches hit a wall. Your body adapts, your calorie burn decreases, and progress stalls. Strength training works on progressive overload — you gradually increase the challenge, so your body keeps responding. There's no plateau if your program is built properly.

None of this means cardio is bad. It's essential for heart health, mental health, and overall fitness. But if your goal is to lose fat and actually change how your body looks, cardio is the supporting act — not the headline.

Every client I work with at Doherty's Gym in Perth — and every online client across Australia — gets a program that combines both strength training and targeted cardio, alongside a complete nutrition plan. Here's what a typical week looks like for someone focused on fat loss:

Three to four strength training sessions per week, each lasting 45–60 minutes. These sessions are programmed around compound movements — squats, deadlifts, presses, rows — that work multiple muscle groups at once and burn more energy than isolation exercises.

One to two cardio sessions per week, targeted to your level. This might be a 20-minute incline walk, a short interval session, or even a weekend hike. The cardio is there to support your deficit and your cardiovascular health — not to be the primary driver of fat loss.

Daily movement outside the gym. I encourage all my clients to aim for 7,000–10,000 steps per day. This non-exercise activity (called NEAT) actually contributes more to your daily calorie burn than your gym sessions do.

And critically — a nutrition plan that supports the training. You can't out-train a bad diet. Every Defined Bodies client gets a personalised nutrition plan with calorie and macro targets, meal guides, and ongoing adjustments as they progress. The training creates the stimulus. The nutrition creates the deficit. Together, they create the results.

This is the question I hear most often from women who are ready to make a change but feel intimidated by the weights area. And I completely get it — the gym can feel overwhelming when you don't know what you're doing.

The answer is simple: you start with a coach who builds your program from scratch based on where you are right now, not where you "should" be. That's exactly what I do with every new client.

If you're in Perth, we train together in person at Doherty's Gym — I'll teach you every movement, correct your form in real time, and progress you at the right pace. If you're anywhere in Australia, my online coaching program gives you a fully custom program with video guidance and weekly check-ins to keep you on track.

You don't need to know anything about lifting before your first session. You just need to show up.