Should You Do Cardio on an Empty Stomach for Fat Loss?
Fasted cardio sounds like it should work better for fat loss. If you wake up, skip breakfast and do cardio before eating, your body has less incoming energy available. So, in theory, it should have to rely more on stored body fat for fuel. That idea is simple, appealing and easy to market.
The problem is that fat loss does not come down to what fuel you burn during one workout. It comes down to what happens over the full day, the full week and the full diet. Fasted cardio may increase the amount of fat you use during the workout itself, but that does not automatically mean you lose more body fat over time. Once calories, training volume and consistency are accounted for, the research does not show a clear fat-loss advantage from doing cardio on an empty stomach.
So the better question is not whether fasted cardio “burns fat.” The better question is whether it helps you lose more body fat than doing the same cardio after eating. Based on the evidence, the answer appears to be no.
What Is Fasted Cardio?
Fasted cardio usually means doing cardio after an overnight fast, before eating breakfast. For example, someone might wake up, drink water or black coffee, then do steady-state cardio, intervals or another form of aerobic exercise before their first meal. Fed cardio is simply cardio done after eating.
The claim is that fasted cardio leads to greater fat loss because the body uses more fat during the workout. That part may be partly true in the short term. Fasted exercise can increase fat oxidation during the session. In plain English, that means you may burn a higher percentage of fat as fuel during that workout. That does not automatically mean you lose more body fat.
Burning Fat During Cardio Is Not the Same as Losing Body Fat
This is the key point: your body uses different fuels throughout the day. Sometimes it uses more carbohydrate. Sometimes it uses more fat. That can change based on what you ate, when you ate, how hard you trained, how long you trained and what your overall calorie intake looks like.
Fasted cardio may increase fat use during the workout itself, but your body can compensate later by using less fat and more carbohydrate at other times. So the real question is not whether you burn more fat during fasted cardio. The better question is whether you lose more body fat over time when cardio is done fasted instead of fed.
Based on the research, the answer appears to be no.
What the Research Shows
One study looked at 20 young women who were placed on customized calorie-restricted diets. Both groups performed one hour of morning cardio three times per week. Each session included a 5-minute warm-up and cool-down at 50% of maximal heart rate. The main part of the workout was 50 minutes of steady-state cardio at 70% of maximal heart rate.
One group did cardio after an overnight fast. The other group did cardio after eating. After four weeks, both groups lost weight and body fat. There was no significant difference between the fasted and fed groups. In other words, when calories and cardio were controlled, doing cardio on an empty stomach did not produce greater fat loss. [1]
Another study looked at overweight women performing interval training. The women completed 10 intervals on a stationary bike. Each interval included 60 seconds of hard cycling at 90% of maximal heart rate, followed by 60 seconds of rest or slow pedalling. They did this three times per week for six weeks. Again, one group trained fasted and the other trained fed.
Both groups lost body fat, but there was no significant difference between them. The fasted group did not lose more fat simply because they trained on an empty stomach. [2]
Later, a systematic review and meta-analysis looked at the broader research on overnight-fasted exercise, weight loss and body composition. The review found that fasted exercise did not lead to greater weight loss or better changes in lean mass or fat mass compared to fed exercise. [3]
More recent research points in the same general direction. A 2023 study in overweight and obese young men found that six weeks of fasted and non-fasted aerobic exercise both improved body shape markers. The fasted group did show a greater reduction in fasting insulin, which may be relevant for metabolic health, but the study still did not show that fasted cardio was clearly superior for fat loss. [4]
A 2025 systematic review and meta-analysis also looked at acute fasted versus fed exercise and markers of glucose and lipid metabolism. It found some short-term differences in glucose, insulin and free fatty acid responses, but those acute changes should not be confused with long-term fat loss. [5] That’s the point most people miss: fasted cardio can change what fuel you use during the workout, but that does not mean it produces more fat loss over time.
Why Fasted Cardio Still Works for Some People
This does not mean fasted cardio is useless. It can still be a good option if it fits your schedule and helps you stay consistent. Some people prefer training first thing in the morning before eating. They feel better, it’s easier to get it done and it prevents the day from getting in the way.
In that case, fasted cardio is fine. The issue is when fasted cardio gets treated like a fat-loss shortcut. It is not. If doing cardio before breakfast helps you stick to your plan, use it. If it makes you feel weak, light-headed, hungry all day or causes you to train with less effort, there is no special reason to force it.
When Fed Cardio May Be the Better Choice
Fed cardio may be the better option if eating beforehand improves your performance. This matters more when the cardio is harder. If you’re doing intervals, high-intensity work or a longer session, having some food in your system may help you train harder, maintain intensity and feel better during the workout.
That may matter more than whether the session is technically fasted. A better workout that you can repeat consistently is usually more valuable than forcing fasted cardio just because it sounds more “fat-burning.”
The Practical Takeaway
Fasted cardio is not magic. Fed cardio is not inferior. For fat loss, the bigger factors are maintaining an appropriate calorie deficit, getting enough protein, following a plan you can stick to, doing enough total activity, training consistently and avoiding approaches that make hunger or adherence worse.
Whether cardio is done before or after eating is a smaller detail. So, should you do cardio on an empty stomach for fat loss? You can, but you don’t need to. Choose the option that fits your schedule, supports your performance and helps you stay consistent. If that means walking before breakfast, great. If that means eating first and training later, that works too.
The key is not whether your stomach is empty. The key is whether your plan is something you can actually follow.
And now you know. 🙂
References
Schoenfeld, B. J., et al. (2014). Body composition changes associated with fasted versus non-fasted aerobic exercise. Journal of the International Society of Sports Nutrition, 11, 54. PubMed.
Gillen, J. B., et al. (2013). Interval training in the fed or fasted state improves body composition and muscle oxidative capacity in overweight women. Obesity, 21(11), 2249-2255. PubMed.
Hackett, D., et al. (2017). Effect of overnight fasted exercise on weight loss and body composition: A systematic review and meta-analysis. Journal of Functional Morphology and Kinesiology, 2(4), 43. Study.
Liu, X., et al. (2023). The effects of six weeks of fasted aerobic exercise on body shape and blood biochemical indexes in overweight and obese young adult males. Healthcare, 11(1), 71. PubMed.
Kazeminasab, F., et al. (2025). The effects of acute bouts of exercise in fasted vs. fed states on glucose and lipid metabolism in healthy adults: A systematic review and meta-analysis of randomized clinical trials. Clinical Nutrition ESPEN, 66, 424-434. PubMed.