Cardio vs weights: which is better for fat loss (what the trials show)

What the trial that compared all three options found

The most cited study is STRRIDE AT/RT (Willis et al., Journal of Applied Physiology, 2012). It randomly assigned sedentary adults with overweight or obesity to three 8-month programmes, without any diet: cardio (the equivalent of about 12 miles, or 19 km, per week at 65-80% of peak oxygen uptake, about 133 minutes a week), weights (3 days, 3 sets of 8-12 reps on 8 machines, about 180 minutes) and both programmes together. 119 people finished with complete data. These were the average changes:

How to read the table: cardio and the combination lost more fat than weights alone, but the difference between those two was not statistically significant, and the combination took more than twice the time. Weights alone barely moved fat, but added the most muscle. The combination achieved both, which is why it lowered body fat percentage and waist size more than any other group. The authors concluded that cardio is the most efficient option for losing fat and weight, and that strength training is needed to gain lean mass.

What later meta-analyses say

Willis is not an isolated case. The meta-analysis by Lafontant et al. (Journal of the International Society of Sports Nutrition, 2025; 36 trials, 1,564 people) reached the same picture: in programmes of 10 weeks or more, cardio removed 1.1 kg more fat and 1.8 kg more body weight than strength training, but kept 0.9 kg less fat-free mass; combined training removed 1.1 kg more fat than strength alone. There were no differences between modes in body fat percentage, none in programmes shorter than 10 weeks, and when the workload was matched all three gave similar results. And adding cardio does not hold muscle back: the Schumann et al. meta-analysis (Sports Medicine, 2022; 43 studies) found that combined training did not reduce muscle growth or maximal strength compared with weights only; only explosive strength was somewhat lower when both were done in the same session.

How many calories each one burns: table for 70 kg

The MET values in the Compendium of Physical Activities (Ainsworth et al., 2011) let you estimate the burn with a simple formula: kcal ≈ MET × body weight in kg × hours. For a 70 kg person (the figures include what you would burn at rest anyway, about 35 kcal per half hour):

In plain terms: half an hour of typical weight training burns about 120 kcal and half an hour of easy running about 290. The extra burn afterwards (EPOC) is real but small: even after very demanding sessions it is only 6-15% of the net cost of the exercise (LaForgia et al., 2006). And the muscle you gain adds little at rest: about 13 kcal a day per kilo (Wang et al., 2010). Weights do not win by burning more; they win by what they protect. Enter your own weight and activity in the calories burned calculator to get your number.

Why weights matter even though they burn less

When you lose weight, not everything you lose is fat. In Willis, the cardio-only group lost weight without gaining lean mass, while both groups that lifted added about a kilo. That kilo does not supercharge your metabolism — it is about 13 kcal a day — but it does show up as strength, function and the shape of your body as fat comes off. If your goal is “look better” and not just “weigh less”, strength training is essential:

• It keeps or increases lean mass while you are in a deficit.
• It improves strength, which is lost with age if you do not train it.
• It lowers body fat percentage even when the scale barely moves.
• The WHO recommends it for all adults, at least 2 days a week.

What the WHO recommends

The 2020 WHO guidelines (Bull et al., British Journal of Sports Medicine) ask adults for 150-300 minutes a week of moderate aerobic activity, or 75-150 minutes of vigorous activity (or an equivalent combination), plus muscle-strengthening activities of moderate or greater intensity that work all the major muscle groups on 2 or more days a week. In other words, the official recommendation already is “both”. Going beyond 300 minutes brings additional health benefits, but you do not need it to get started. To find out what “moderate” means for you, work out your zones with the heart rate zone calculator.

How to combine them in one week

A week that meets the WHO guidelines and fits a normal schedule, with about 4 hours in total:

• If you do strength and cardio on the same day, put first whatever matters most to you; if it is getting stronger, lift first or separate them by a few hours.
• Short on time? Interval training (HIIT) achieved the same fat loss as continuous cardio with about 40% less training time in the Wewege (2017) meta-analysis, although it is harder.
• A third strength day helps if you tolerate it. To start, a 2-3 day full-body routine for beginners covers the whole body.
• Steps count too: 5,000 extra steps are about 50 minutes at a normal pace (3.5 MET), roughly 145 net kcal for 70 kg.

Diet matters more than training

Half an hour of easy running is about 290 kcal for 70 kg, and it is far easier to eat that than to burn it. That is why exercise works better as a partner to a moderate dietary deficit than as a substitute: in Willis, without any diet change, eight months of cardio removed 1.7 kg of fat on average. Useful, but modest. To see both halves of the balance, Renzy estimates the calories and macros of each meal from a photo (and you can correct them), and it scans the barcode of packaged foods.