For moving the number on the scale, cardio usually wins: it burns more calories per session, and in head-to-head trials it produces more weight and fat loss than lifting alone. Strength training wins on what that weight is made of. It helps you keep, or even build, muscle while you lose fat. The best plan for most people uses both, with your diet doing most of the work on the calorie deficit.
What the Research Says
The clearest head-to-head comparison is the STRRIDE AT/RT trial. Researchers randomly assigned 119 sedentary, overweight or obese adults to eight months of aerobic training, resistance training, or both (Willis et al., 2012):
| Aerobic only | Resistance only | Both | |
|---|---|---|---|
| Body weight and fat mass | Reduced more than resistance only | Least reduction | Reduced more than resistance only |
| Lean mass | Least change | Increased more than aerobic only | Increased more than aerobic only |
| Time required | Moderate | Moderate | About double |
The authors concluded that aerobic training is the most efficient way to reduce fat and body mass, while a program that includes resistance training is needed to increase lean mass.
Resistance training still burns fat.
And the American College of Sports Medicine's position on weight loss puts it this way: resistance training doesn't enhance weight loss, but it may increase fat-free mass and increase loss of fat mass (Donnelly et al., 2009).
Why Cardio Moves the Scale Faster
Running, cycling, rowing, and brisk walking keep large muscle groups working continuously, so a cardio session usually burns more calories than a lifting session of the same length, where much of the time goes to rest between sets.
That adds up over a week. The ACSM position stand found that 150 to 250 minutes a week of moderate activity produces only modest weight loss, while more than 250 minutes a week is associated with clinically significant weight loss. Observational studies also link more than 250 minutes a week with keeping weight off afterward, though the ACSM found no well-designed randomized trials to confirm it.
Cardio also improves your heart and aerobic fitness directly, which matters for health whether or not the scale moves. If you're worried that easy cardio is a waste of time, or that you have to stay in a "fat-burning zone", see why the fat-burning zone is a myth.
Why Strength Training Still Matters
When you eat less than you burn, your body doesn't only lose fat. Without a reason to keep it, it also gives up some muscle. Resistance training is that reason: it signals that the muscle is still needed, so more of what you lose comes from fat.
That matters for a few reasons:
- Strength and function. Keeping muscle keeps you strong for everyday life and for the training you enjoy. In a trial of dieting adults with obesity aged 65 and over, combining aerobic and resistance exercise improved physical function more than either one alone (Villareal et al., 2017).
- What the scale doesn't show. A pound of muscle weighs the same as a pound of fat, but muscle is denser, so it takes up less space. Two people at the same weight can look and feel very different depending on how much of that weight is muscle.
- Metabolism, honestly. Muscle burns somewhat more energy at rest than fat, but the difference is small. Lifting won't turn your metabolism into a furnace; its main job during weight loss is protecting the muscle you have.
Losing weight fast, or with a medication like a GLP-1, makes this even more important. Our guide to keeping muscle on a GLP-1 covers protein and strength training in more detail.
Can You Lose Weight Without Cardio?
Yes. Weight loss comes from a calorie deficit, and you can create one through diet alone. Cardio makes the deficit easier to reach and brings its own heart health benefits, but it isn't mandatory.
What you shouldn't skip is some form of resistance training. If you hate cardio, lift, walk more during the day, and let your diet handle the deficit. You'll lose fat while protecting the muscle you have.
How to Combine Strength and Cardio
The U.S. Physical Activity Guidelines recommend at least 150 to 300 minutes of moderate aerobic activity a week, plus muscle-strengthening activity on two or more days. For weight loss, that's a good starting point:
- Lift two to three times a week (three or more if you're on a GLP-1). Cover your major muscle groups (legs, back, chest, shoulders, arms, core) and add weight or reps over time.
- Do cardio on most days. Mostly easy to moderate sessions you can repeat, such as Zone 2 training, with a harder interval session once or twice a week if you enjoy them.
- Keep the deficit moderate. A slower, steadier pace makes it easier to keep both your training quality and your muscle.
How FITIV Helps You Balance Both
FITIV Pulse tracks your lifting and your cardio in one app, so you can see the whole week instead of two separate logs.
- Strength sessions, set by set. Log exercises, sets, reps, and weight on your iPhone or Apple Watch, then see how each session's sets split across muscle groups. Learn more about the workout builder.
- One training load for both. Runs, rides, and lifting sessions all count toward the same training load through your heart rate, so you can see when you're building fitness and when you're piling on fatigue.
- Weight trends instead of daily noise. Set a goal weight and pace in Weight Management, and track a 7-day moving average that smooths out the day-to-day swings from water and food.
- Your energy balance. The Energy card compares the calories you burn (active plus resting, from Apple Health) with the calories you log in a food app that saves to Apple Health, and shows the difference as a deficit or surplus.
Frequently Asked Questions
Does lifting weights make you gain weight?
It can add a little lean mass over time, especially if you're new to training, so the scale may move more slowly than your waistline. That's usually a good trade: you're losing fat and keeping muscle. Watch your trend over several weeks rather than any single weigh-in.
How much cardio do I need to lose weight?
The American College of Sports Medicine found that 150 to 250 minutes of moderate activity a week brings modest weight loss, and more than 250 minutes a week is linked to clinically significant weight loss. Combining exercise with a moderate calorie deficit works better than either one alone.
Will strength training speed up my metabolism?
Only a little. Muscle uses somewhat more energy at rest than fat, but the difference is small. The bigger benefit during weight loss is that strength training helps you hold on to muscle, so more of the weight you lose is fat.
Can you lose fat and build muscle at the same time?
Often, yes, especially if you're new to lifting or returning after a break. Resistance training with enough protein can increase lean mass while you lose fat, though the gains slow down as you get more experienced or as your calorie deficit gets larger.
