Cardio before or after weights? Fasted cardio, and how much it burns

By the Voltra team · Updated 6 October 2026

Before or after weights?

A 2018 meta-analysis pooled 10 studies of healthy adults who did cardio and weights in the same session for at least 5 weeks. Lifting first, then cardio, gave a 6.91% bigger gain in lower-body dynamic strength than the reverse order [2]. The order made no difference to lower-body muscle size, static strength, maximal aerobic capacity (VO2max) or body fat percentage [2].

So if you do both in one visit to the gym, lift first; the order didn't cost aerobic fitness. If your sport needs jumping or sprinting, keep them at least 3 hours apart: in the meta-analysis below, cardio held back explosive strength mainly when it was done in the same session [1].

Does cardio kill your gains?

Not muscle size or maximal strength. A 2022 meta-analysis of 43 studies compared strength training plus cardio with the same strength training alone, for at least 4 weeks [1]:

SMD is the standardised mean difference; 0 means no difference [1].

Explosive strength is how fast you produce force, as in a jump. Its gains were held back most when cardio and weights were in the same session, 20 minutes or less apart, and not significantly when they were at least 3 hours apart [1]. The results didn't depend on whether the cardio was running or cycling, on training more or fewer than 5 times a week, on whether people were untrained or already active, or on being under or over 40 [1].

Fasted cardio, on an empty stomach

Cardio after an overnight fast does burn more fat during the session: a 2016 meta-analysis of 27 studies found about 3 g more fat burned than when people had eaten first [3]. That didn't turn into more fat loss over weeks. In a 4-week trial, 20 young women on a calorie deficit did an hour of steady cardio three times a week, either fasted or after a meal; both groups lost weight and fat, with no difference between them [4].

With the diet held the same, being fasted made no difference, so train fasted or fed, whichever lets you train better. The trial was small and included only women. For training while fasting in Ramadan, see Ramadan: eating, training and staying hydrated while fasting.

How many calories cardio burns

The 2024 Adult Compendium of Physical Activities gives each activity a MET value: how many times your resting energy use it takes [5][6]. One MET is about 1 kcal per kg of body weight per hour [5], so:

kcal = MET × your weight in kg × hours

At 80 kg, an hour of brisk walking (4.8 MET) is 4.8 × 80 × 1 = 384 kcal, and half an hour of jump rope (11.0 MET) is 11 × 80 × 0.5 = 440 kcal (calculated).

kcal per 30 minutes, calculated with the formula above from the Compendium's MET values [5]. The Compendium gives the running speed as 6 to 6.3 mph, which we converted. On the WHO's scale, 3 to under 6 METs is moderate and 6 or more is vigorous [8].

These are gross figures: they include the 1 MET you'd burn sitting still anyway. What the exercise adds is (MET − 1) × kg × hours, so the 80 kg hour of brisk walking adds about 304 kcal over resting (calculated). The Compendium also says its values weren't developed to give one person's exact burn: they assume a standard resting rate, so yours can be higher or lower [5].

HIIT or steady cardio?

For fat loss, the difference is mostly time. A 2017 meta-analysis of 13 trials in overweight and obese adults aged 18 to 45, averaging 10 weeks of three sessions a week, found that high-intensity interval training (HIIT) and steady moderate-intensity cardio both reduced whole-body fat and waist size, with no significant difference between them; HIIT took about 40% less training time [7]. In those trials, running cut fat mass with either method, while cycling didn't produce fat loss [7].

How much cardio a week

The WHO recommends that adults do 150 to 300 minutes of moderate aerobic activity a week, or 75 to 150 minutes of vigorous activity, or a mix, plus muscle strengthening on 2 or more days a week [8]. Going beyond 300 minutes of moderate activity may bring additional health benefits [8]. Brisk walking (4.8 MET) counts as moderate, and running or jump rope as vigorous [5][8].

More on this: how much exercise you need a week, Zone 2 cardio, how many steps a day and Japanese walking. In the summer heat, read exercising in the heat first. Whether cardio or ab work trims the belly in particular is covered in Can ab exercises burn belly fat?

In Voltra

In the Train tab, the Cardio page shows this week's cardio minutes as a ring against a weekly target that follows the cardio level you chose: 150 minutes for moderate, 75 for vigorous and 175 for light. Next to it are the week's sessions, calories burned and kilometres. If you've connected Apple Health, cardio workouts recorded there, from a watch for example, count toward the ring along with the sessions you log yourself. To add one by hand, tap Log a session; for intervals, tap Intervals. If you don't enter the calories when you log a session, Voltra estimates them from a set rate per minute for that activity.

Frequently asked

Sources

1. Schumann M, Feuerbacher JF, Sünkeler M, Freitag N, Rønnestad BR, Doma K, Lundberg TR (2022). Compatibility of Concurrent Aerobic and Strength Training for Skeletal Muscle Size and Function: An Updated Systematic Review and Meta-Analysis. Sports Medicine 52(3):601–612. Abstract and results. 43 studies of healthy adults, at least 4 weeks; the same session meant 20 minutes or less apart.
2. Eddens L, van Someren K, Howatson G (2018). The Role of Intra-Session Exercise Sequence in the Interference Effect: A Systematic Review with Meta-Analysis. Sports Medicine 48(1):177–188. Abstract. 10 studies, at least 5 weeks.
3. Vieira AF, Costa RR, Macedo RC, Coconcelli L, Kruel LF (2016). Effects of aerobic exercise performed in fasted v. fed state on fat and carbohydrate metabolism in adults: a systematic review and meta-analysis. British Journal of Nutrition 116(7):1153–1164. Abstract. 27 studies, 273 participants; fat burned during exercise.
4. Schoenfeld BJ, Aragon AA, Wilborn CD, Krieger JW, Sonmez GT (2014). Body composition changes associated with fasted versus non-fasted aerobic exercise. Journal of the International Society of Sports Nutrition 11:54. Abstract. 20 young women on a calorie deficit, 4 weeks.
5. Compendium of Physical Activities (2024). 2024 Adult Compendium. Pages used: Walking, Running, Bicycling, Conditioning exercise, Water activities, Unit conversions and Corrected METs. Codes, in table order: 17355, 17358, 17361, 17035, 12020, 12050, 01200, 01270, 02048, 02071, 02065, 02068, 02210, 02214, 18240, 02054.
6. Herrmann SD, Willis EA, Ainsworth BE, et al. (2024). 2024 Adult Compendium of Physical Activities: A third update of the energy costs of human activities. Journal of Sport and Health Science 13(1):6–12. Abstract.
7. Wewege M, van den Berg R, Ward RE, Keech A (2017). The effects of high-intensity interval training vs. moderate-intensity continuous training on body composition in overweight and obese adults: a systematic review and meta-analysis. Obesity Reviews 18(6):635–646. Abstract. 13 trials, ages 18 to 45.
8. Bull FC, Al-Ansari SS, Biddle S, et al. (2020). World Health Organization 2020 guidelines on physical activity and sedentary behaviour. British Journal of Sports Medicine 54(24):1451–1462. Recommendations for adults; glossary for moderate and vigorous intensity.

Sources checked on 6 October 2026.

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