Is it better to run on an empty stomach to boost fat burning or to jog at a low heart rate to stay in the right “zone”? Or, should we do short but exhausting intervals to fight off those extra pounds? Today, I want to shed a light on how to best burn fat while running.
What does fat burning mean?
Fat burning refers to the ability of our bodies to oxidize or burn fat and use fat as fuel instead of carbohydrates. This is an aerobic process – fat is broken down with the help of oxygen. In general, more fat is burned during aerobic activities like Nordic walking, running, or biking.
When do we burn fat?
The body uses both fat and carbohydrate reserves as fuel during all kinds of activities. However, the percentage of energy coming from fat can be higher or lower depending on the type of activity.
In general, more fat is burned:
- During low-intensity physical activities
- During longer activities – the longer the activity, the higher the percentage of burned fat
- If you are in better shape overall – the fitter you are, the better you can use fat as fuel
More fat burned ≠ more weight loss. Weight loss depends mostly on the total amount of calories you burn, not just the percentage of fat burned during the activity.
Get You hands on this Guide
Burn more fat when running
You burn fat ideally while running at a pace where you would be able to maintain a full conversation. That’s when fat becomes your primary source of fuel. According to experts, this should be a pace that you would theoretically be able to maintain for up to 8 hours, i.e. slow!
Run 30 minutes to burn fat?
A slow, low-intensity run uses more fat for fuel but takes longer to burn a lot of calories in total. That’s why it’s advised to run longer than 30 minutes when running at a low-intensity. However, a faster, high-intensity run can burn more calories in a shorter time period. And even if just a small percentage of those calories come from fat, it can still significantly boost your weight loss!
Plus, you can benefit from losing body fat even after you run as your body keeps burning fat for 2 to 3 hours after finishing a run. If you want to shed a few pounds, make sure you only ingest liquids and maybe a little protein during that time frame.
High-intensity running and fat burn
High-intensity training pushes our heart rate up until we reach the anaerobic zone. During high-intensity runs the percentage of fat burned is lower because our bodies resort to our carbohydrate reserves.
However, due to the intense exercise, the total calorie consumption is higher. We burn more calories due to the hard muscle work – even AFTER the run. The body needs more energy for recovery, thereby burning even more calories. That’s how you benefit from post-workout fat burning and the afterburn effect (EPOC, excess post-exercise oxygen consumption).
What burns more fat?
What’s better? A longer, yet slower “fat-burning run” or a few sprints at a higher heart rate? On the one hand, during a slower run, you’re in the ideal fat burning zone. On the other hand, intense interval training challenges your muscles even more.
In my opinion, a possible solution would be to combine both slower, relaxed runs in the aerobic zone (where it’s easy to maintain a conversation while running) and short, intense interval runs (which should be done only about once per week anyway).
Running on an empty stomach
If you feel fit enough for a slow, pre-breakfast run to improve your fat metabolism, do it:
- In the morning, on an empty stomach – 40 minutes max.
- At a max. oxygen consumption (VO2 max) of 50-60%*
* These values are estimates. You can determine your individual, ideal workout intensity through a lactate test.
Whether your body burns fat efficiently or not depends on the right diet and on your sleep quality, too, as fat burning takes place 24/7, especially when you’re fast asleep.