If you’ve ever wondered whether fasted cardio is superior for fat loss, you’re not alone. This is a common belief among athletes, bodybuilders, and fitness enthusiasts, but what does the science actually say?

The Theory Behind Fasted Cardio

Fasted cardio refers to performing cardiovascular exercise on an empty stomach, typically in the morning before eating. The rationale behind this approach is that low glycogen levels will shift the body’s energy utilization away from carbohydrates and instead mobilize stored fat for fuel. While this may sound promising in theory, fat oxidation during exercise is not the same as actual body fat loss.

What the Research Shows

Yes, fasted cardio leads to increased fat utilization during the workout itself. However, research suggests that the body compensates for this by reducing fat oxidation for the remainder of the day.

A systematic review and meta-analysis of studies found no significant differences in weight loss or body composition between individuals who performed cardio in a fasted versus a fed state. Ultimately, whether you exercise before or after eating does not appear to impact fat loss in the long run.

Which Should You Do?

While fasted cardio is not inherently better for fat loss, it’s also not harmful. If you enjoy doing cardio on an empty stomach and feel good doing it, there’s no reason to stop. However, if you perform better with food in your system, there’s no fat loss disadvantage to exercising after a meal.

What About Performance?

One area where training in a carb-restricted state might have benefits is in endurance adaptations. Some endurance athletes use a “train low, compete high” approach—training in a low-glycogen state for some sessions while ensuring high glycogen availability for intense workouts. This is a more nuanced strategy that applies to specific training goals rather than general fat loss.

The Bottom Line

Fasted cardio is not superior for fat loss, but it’s also not detrimental. How you choose to do cardio should depend on personal preference and how you feel during your workouts. The key to fat loss remains consistent energy balance—burning more calories than you consume over time.

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