Skip to content
  1. free shipping on all usa orders over $75
does fasted cardio work

What Is Fasted Cardio And Does It Work For Fat Loss

Let’s talk about fasted cardio—a hot topic in the endurance world. You’ve probably heard people rave about doing cardio on an empty stomach to burn fat faster. Maybe you’ve even tried it yourself, rolling out of bed and heading straight into a run or ride without breakfast. But does it really work, or is it just another fitness myth? The quick answer: not exactly. Let’s break down why fasted cardio might not be the fat-burning miracle it’s cracked up to be.

What Is Fasted Cardio?

Fasted cardio is just what it sounds like: doing aerobic exercise in a fasted state, usually after 10 to 14 hours without eating (like first thing in the morning). Some people claim it’s the key to torching fat because, with low glycogen stores, your body has no choice but to burn fat for fuel. Sounds logical, right? But, as usual, the devil’s in the details.

Does Fasted Cardio Really Burn More Fat?

At face value, yes, fasted cardio does burn more fat during the workout. A 2016 meta-analysis found that fasted cardio significantly increased fat oxidation compared to fed cardio . But here’s the thing—you’re not just trying to burn fat during a 30-minute run. You care about your overall body composition and performance, and that’s where fasted cardio starts to lose its luster.

It’s Not About the Snapshot, It’s About the Big Picture

Your body doesn’t operate in a vacuum. What happens during a single workout is just one piece of the puzzle. How your body uses fuel—whether it's carbs, fat, or protein—depends on a range of factors like exercise intensity, duration, and your fitness level. And, crucially, fat loss should be measured over days and weeks, not just one workout session .

Here’s a rule of thumb: if you burn more carbs during a workout, you’ll burn more fat afterward. Conversely, if you burn more fat during exercise (as in fasted cardio), you’ll burn more carbs later . So while fasted cardio might seem effective in the moment, it balances out over a 24-hour period.

Research: Fasted Cardio Isn’t a Fat-Loss Game Changer

A 2014 study took a hard look at fasted versus fed cardio. Over three weeks, two groups of women either did fasted or fed workouts. Both groups lost weight and fat, but here’s the kicker: there was no significant difference between the two . So while fasted cardio might feel like it's working wonders, the long-term results don’t really back up the hype.

Fitness Level and Intensity Matter

Here’s another twist: fasted cardio might work better for some than others. For example, if you’re a beginner or doing low-intensity workouts, you might burn more fat during a fasted session. But once you start cranking up the intensity, things change. Research shows that during moderate to high-intensity exercise, the body breaks down more fat than it can actually use, meaning the leftover fat just gets stored again .

Not All Fat Burned Is the Fat You Want Gone

Here’s a curveball: the fat you burn during fasted exercise isn’t necessarily the fat you’re looking to lose. Studies show that up to 50% of the fat burned in untrained individuals during fasted exercise comes from intramuscular triglycerides (IMTGs)—tiny fat droplets stored in your muscles . IMTGs aren’t the subcutaneous fat you see in the mirror, so don’t expect to see your love handles disappear after a few fasted workouts.

So, What’s the Best Way to Burn Fat?

If your goal is fat loss, you’re better off focusing on high-intensity interval training (HIIT) rather than relying on fasted cardio. Studies consistently show that HIIT is more effective for fat loss than steady-state cardio, even if it burns fewer calories from fat during the actual workout. Why? Because HIIT cranks up your metabolism for hours after you’re done, helping you burn more fat over the long haul .

Carbs Are Your Friend for Performance

You might think, “Well, I can just do HIIT in a fasted state!” But here’s the problem: to truly crush a HIIT workout, you need carbs. A study with well-trained cyclists found that when they exercised at 70% VO2 max, those who had carbs before and during the workout outperformed the fasted group by up to 46% . So if you want to hit those high intensities that drive fat loss, you’ll need some fuel in the tank.

The Bottom Line

If you like doing fasted cardio and it fits your schedule, go for it. But don’t expect it to be a magic bullet for fat loss. The research just doesn’t back that up. On the other hand, high-intensity training—especially when fueled properly—can help you burn more fat and improve performance over time.

 

References:

  • Boesch C, Slotboom J, Hoppeler H, and Kreis R. In vivo determination of intramyocellular lipids in human muscle by means of localized H-MR-spectroscopy. Mag Reson Med 37: 484-493, 1997.
  • Civitarese AE, Hesselink MK, Russell AP, Ravussin E, and Schrauwen P. Glucose ingestion during exercise blunts exercise-induced gene expression of skeletal muscle fat oxidative genes. Am J Physiol Endocrinol Metab 289: E1023-E1029, 2005.
  • Coyle EF, Hagberg JM, Hurley BF, Martin WH, Ehsani AA, and Holloszy JO. Carbohydrates during prolonged strenuous exercise can delay fatigue. J Appl Physiol 59: 429-433, 1983.
  • Febbraio MA, Chiu A, Angus DJ, Arkinstall MJ, and Hawley JA. Effects of carbohydrate ingestion before and during exercise on glucose kinetics and performance. J Appl Physiol 89: 2220-2226, 2000.
  • Goodpaster BH, He J, Watkins S, and Kelley DE. Skeletal muscle lipid content and insulin resistance: evidence for a paradox in endurance-trained athletes. J Clin Endocrinol Metab 86: 5755-5761, 2001.
  • Hansen, K., Shriver, T. & Schoeller, D. The Effects of Exercise on the Storage and Oxidation of Dietary Fat. Sports Med 35, 363–373 (2005). https://doi.org/10.2165/00007256-200535050-00001
  • Horowitz JF1, Mora-Rodriguez R, Byerley LO, Coyle EF.Lipolytic suppression following carbohydrate ingestion limits fat oxidation during exercise.Am J Physiol. 1997 Oct;273(4):E768-75. doi: 10.1152/ajpendo.1997.273.4.E768.DOI:1152/ajpendo.1997.273.4.E768
  • Hutchingson, Alex. Adapting to Burn Fat as Fue Runner’s World. 2015.
  • Mateo, Ashley. What is Fasted Cardio--and is it a Good Idea to Run on Empty? Runner’s World. 2020.
  • SCHABORT, ELSKE J.; BOSCH, ANDREW N.; WELTAN, SANDY M.; NOAKES, TIMOTHY D. The effect of a preexercise meal on time to fatigue during prolonged cycling exercise. Medicine & Science in Sports & Exercise: March 1999 - Volume 31 - Issue 3 - p 464-471.
  • Schoenfeld, B.J., Aragon, A.A., Wilborn, C.D. et al. Body composition changes associated with fasted versus non-fasted aerobic exercise. J Int Soc Sports Nutr 11, 54 (2014). https://doi.org/10.1186/s12970-014-0054-7
  • Schoenfeld, Brad MS, CSCS. Does Cardio After an Overnight Fast Maximize Fat Loss? Strength and Conditioning Journal: February 2011 - Volume 33 - Issue 1 - p 23-25
  • doi: 10.1519/SSC.0b013e31820396ec
  • Sonko BJ1, Fennessey PV, Donnelly JE, Bessesen D, Sharp TA, Jacobsen DJ, Jones RH, Hill JO.Ingested fat oxidation contributes 8% of 24-h total energy expenditure in moderately obese subjects. J Nutr. 2005 Sep;135(9):2159-65. DOI:1093/jn/135.9.2159
  • van Loon LJ. Use of intramuscular triacylglycerol as a substrate source during exercise in humans. J Appl Physiol 97: 1170-1187, 2004.
  • Vieira AF1, Costa RR2, Macedo RC2, Coconcelli L2, Kruel LF2.Effects of aerobic exercise performed in fasted v. fed state on fat and carbohydrate metabolism in adults: a systematic review and meta-analysis.Br J Nutr. 2016 Oct;116(7):1153-1164. Epub 2016 Sep 9.
  • Wright DA1, Sherman WM, Dernbach AR.Carbohydrate feedings before, during, or in combination improve cycling endurance performance.J Appl Physiol (1985). 1991 Sep;71(3):1082-8.DOI:1152/jappl.1991.71.3.1082
  • Zhang H, Tong TK, Qiu W, et al. Comparable Effects of High-Intensity Interval Training and Prolonged Continuous Exercise Training on Abdominal Visceral Fat Reduction in Obese Young Women. J Diabetes Res. 2017;2017:5071740. doi:10.1155/2017/5071740