Fasted Cardio and Fat Loss: Unpacking the Science.
Fasted cardio—exercising on an empty stomach, usually first thing in the morning—has become a popular strategy for fat loss. The idea is that by working out after an overnight fast, your body will burn fat for fuel instead of relying on glycogen (stored carbs).
When you wake up in the morning, your body has already been fasting for hours. Your glycogen stores (your body’s main source of energy) are lower, which means there’s less readily available glucose to fuel your workout.
As a result, your body may turn to fat as its primary fuel source. This is the main reason people claim that fasted cardio can lead to more fat burning—especially when performing low- to moderate-intensity exercises like jogging or walking.
Research shows that, during fasted cardio, your body does indeed burn a higher percentage of fat during the workout compared to exercising after eating.
However, studies suggest that total fat loss over time doesn’t differ significantly between fasted and fed cardio. Essentially, while fasted cardio might help you burn more fat during the workout itself, it doesn’t necessarily lead to more fat loss overall.
One downside of fasted cardio is that it may affect your performance, especially if you’re doing high-intensity exercise. Without adequate fuel, you might feel sluggish or fatigued, potentially leading to shorter or less intense workouts.
Fasted cardio might offer a slight advantage in terms of fat burning during your workout, but overall fat loss comes down to your calorie balance and workout consistency.
If fasted cardio fits your routine and you feel good doing it, it can be a useful tool. But it’s not a magic bullet—consistency, intensity, and diet remain the most important factors in shedding fat.