Cardio vs. weights for fat loss is one of the oldest debates in fitness. Which is better for losing body fat? A lot of people argue that doing both weights and cardio is ideal for fat loss. Is it true? If it is true, does that bring up another conundrum?:
There’s been a seemingly never-ending debate about whether combining cardio and weight training together kill your results. Specifically, will cardio zap your strength gains and make it harder to gain muscle? If so, and your primary goal is strength and muscle gain, should you just lift and skip the cardio?
A recent study gave us some of the clearest answers to these questions yet because it was a “meta analysis” combining the findings of 31 different studies.
Research results spoiler: When cardio and weight training are programmed properly, you can lose fat while maintaining muscle without major interference – as long as the amount of cardio isn’t excessive…
Which brings up a final question: how much cardio is excessive if you want to maximize fat loss while also keeping your hard earned muscle?
The Cardio Vs. Weights Study: Primary Purpose
The study was led by Kworweinski Lafontant from The University of Central Florida and the results were published in the Journal of the International Society For Sports Nutrition.
The researchers set out to compare how resistance training, aerobic training, and concurrent training affect body composition – specifically lean body mass and fat mass (not just body weight).
Obviously, we already know that resistance training builds muscle and cardio training burns fat. But the questions that are still debated and not completely answered include:
- Which type of exercise burns more fat, cardio or weights?
- What happens when you combine cardio and weights in the same training cycle? (Concurrent training).
How The Study Was Designed
Because this was a meta-analysis, it pooled data from 31 trials with a total of 1564 subjects. That’s a pretty good sample size.
A slight downside is that all these different studies used different training protocols. I mean, when we talk about “resistance training” or “cardio training” think about how many different types of programs there are.
This means we still may not be able to easily pin down one prescription for exercise type, frequency, and duration and call it the best.
However, with a study like this, we can “average things out: and then we get a pretty good idea of overall body composition results and what the range of ideal variables is for lifting and cardio.
The researchers did specify the definitions of each type of training in general:
Aerobic training (AT / cardio): The studies defined AT as continuous, whole-body rhythmic exercise at a moderate-to-vigorous intensity. Cardio was typically treadmill walking or jogging, stationary cycling, or running. Sessions lasted 20 to 45 minutes, and were performed 2 to 5 days per week depending on the trial. This was steady-state cardio, not HIIT or intervals.
Resistance training (RT): RT programs used traditional lifting routines designed to build muscle. That meant multi-joint exercises like presses, rows, and squats, usually performed in 2–4 sets of 8–12 repetitions, with normal rest intervals between sets.
Training frequency was typically 3–4 days per week with some studies involving as little as 2 sessions per week. Importantly, these were not circuit or metabolic-style sessions – the workouts were conventional strength and hypertrophy training.
Concurrent training (CT): CT combined both types of in the same training week. Some studies had participants do cardio and weights on the same day (either before or after each other), while others scheduled them on separate days. The researchers also compared short- vs long-duration programs and whether workloads were “matched” or not (equalized for training volume).
This distinction matters: the results of this meta apply specifically to steady-state cardio combined with standard resistance training. Different outcomes might be expected if, for example, circuit-style lifting (which blends strength and cardio) or HIIT protocols were used. (I’ve always said that circuit resistance training is kind of like “doing cardio with weights”).
Study Results
Resistance training: As expected, lifting weights increased lean body mass and was the superior choice for muscle gain compared to cardio. Fat loss, however, was modest when weights were performed alone.
Aerobic training: Cardio reduced fat mass more effectively than lifting alone, but provided little or no stimulus for building lean mass.
Concurrent training: Doing both cardio and weights produced greater fat loss than resistance training alone, while still promoting muscle retention or gain. In other words, averaging the results of over 30 studies, the feared “interference effect” did not emerge in these trials when cardio was performed in moderate amounts.
The Interference Effect: How Much Cardio Is Too Much?
One of the most common questions lifters ask is: “At what point does cardio start to eat into my gains?”
This study wasn’t designed to directly answer that – it was more about the effect of AT, RT, and CT on body composition. But looking at the training protocols, most involved 2–5 steady-state cardio sessions per week of 20–45 minutes. Within that range, interference with muscle growth wasn’t a problem.
Previous research found similar outcomes: 2 to 4 days per week at 20 to 40 minutes produced no interference (reducing resistance training performance or holding back muscle gains).
Based on this research combined with what I’ve observed in my own concurrent training and in the results of my clients, I think it’s safe to say that up to 4 to 5 cardio sessions of 40 to 45 minutes is not going to hurt your muscle gains.
Some researchers have suggested up to 150 minutes of steady state cardio per week as a safe cutoff. (That’s 30 minutes, 5 days a week).
Problems with interference are more likely when:
- Cardio volume climbs very high (e.g., 6–7 days per week, long durations, competitive endurance training).
- High-impact modalities like running dominate over lower-impact choices like cycling.
- Cardio is performed immediately before lifting, especially if the legs are pre-fatigued.
This matches my personal experience, and I’ll even go as far to say that I think 6 or 7 days a week of cardio for 30 to 45 minutes can be done concurrently with lifting with little to no interference as long as the cardio is low impact.
Having dabbled with endurance training (a couple half marathons), I can confirm that out of all the types of cardio you could do, running (high impact) produces the most interference. Leg day in the gym is a real drag when you’re running long distances on top of the lifting.
But back to the research and the implications for fat loss.
Practical Applications
This study confirmed that combining cardio and weights is superior than doing one or the other if you want to optimize muscle gain and fat loss.
It also showed that for fat loss, the type of cardio doesn’t matter if the calorie burn is equal. That means you can choose the exercise based on your personal preference.
Either way, if your primary goal is fat loss, use concurrent training with the cardio of your choice. This will maximize fat burning while still preserving or building muscle.
Obviously cardio like running will burn a lot more calories per minute than walking. But also keep in mind that high impact cardio like running is more likely to interfere with your lower body lifting sessions.
With low impact, low-intensity types of cardio like walking, you can do a even more volume with no fear of interference at all.
You could get away with just lifting and following a good calorie-restricted diet and lose fat, but that won’t maximize the rate of fat loss. Including some cardio is optimal. (And don’t forget you get health benefits as well, not just increased fat loss).
If your primary goal is muscle gain, then during a muscle gain phase keep doing cardio, but keep the cardio volume moderate and favor low-impact modes like cycling. Make progressive overload resistance training your top priority.
If your primary goal is fat loss, then during your fat loss phase, increase your cardio while keeping up your lifting, but be on the lookout for interference if you choose high impact cardio and or high volume cardio.
For lifters and fat-loss seekers, this study offers reassurance. You don’t need to choose between cardio and weights. In fact, combining both is the smartest approach if your goals are a leaner and more muscular physique.
More good news is that research confirms you can choose the type of cardio you enjoy. If the calorie burn is equal, there won’t be any difference in fat loss. And if you choose cardio you enjoy, you’re more likely to stick with it, and the better you stick with it, the better your fat loss.
I’ll talk more about concurrent training in upcoming blog posts, including my forays into running and long distance backpacking and how that impacted my lifting, along with even more research that focused specifically on concurrent aerobic and resistance training.
-Tom Venuto,
Author of Burn the Fat, Feed the Muscle
Author of Meal Prep For Fat Loss
Founder of Burn the Fat Inner Circle
Scientific References
Lafontant K et al, Comparison of concurrent, resistance, or aerobic training on body fat loss: A systematic review and meta-analysis, Journal of the International Society of Sports Nutrition, 22:1.
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