Is fasted cardio better?

One of the highly-debated topics in fitness is whether you should eat before a cardio workout, particularly if your goal is fat loss. While both sides have plausible arguments, we’re all about SCIENCE here, so let’s break it down.

The thought behind fasted cardio is that if you don’t have any food in your system, your body is forced to rely on stored body fat for energy, resulting in fat loss. And while this makes sense, it’s not quite true…

What’s actually happening is fat burning – better known as “fat oxidation”. During normal daily activity and low-intensity exercise, the body primarily uses fat for energy. However, this does not directly mean “fat loss”. The only way to truly lose body fat is to create a calorie deficit – meaning you utilize more calories throughout the day than you consume. Cardio is one tool that can help contribute to this deficit, but this has nothing to do with whether you use fat or carbs as your main energy source during the workout.

In fact, fasted cardio may actually IMPAIR fat loss! Think about it – burning more calories in the day will create a larger deficit for weight loss; and how do you increase that burn? More effective exercise! Fasting before a workout, especially cardio, limits your energy and effort, creating a lower metabolic impact – especially since higher intensities require carbs. Plus, that hunger will catch up to you and likely lead to higher intakes later in the day.

In the end, it all comes down to personal preference and goals. There’s no magic bullet for fat loss – it simply comes down to that calorie deficit. If your goal is to have a more effective workout or train for an event, it’s better to eat something light beforehand, like a banana, granola bar, or Energy Bites (see prior blog post for recipe). However, if you truly feel better on an empty stomach and your workout is less than an hour long, you’ll be fine without eating beforehand – just make sure you’re doing it for comfort, not fat burning!