The Big Difference Between Burning Calories & Burning Fat?

Running woman with different body mass

Your body burns energy (calories) from either fat or carbohydrates depending on the intensity of your activity.

Now the question is, which energy source (fat or carbohydrates) is better for weight loss and slim down? 

Before going furhter, it’s important to note that calories are calories when it comes weight loss, and you’re going to need to burn calories both from fat and carbohydrates when you’re trying to lose weight. 

Women’s fitness has come a long way since the Jane Fonda days but one thing that still baffles most women is when it comes to weight loss is whether burning fat is better than burning total calories? And are those cardio machines at the gym right with their magic ‘fat burning zones’? 

The answer is a confusing yes, and no. Yes, there is a slight bit of truth to the fat burning zone, however in its usefulness for weight loss, the research has been misinterpreted. 

The concept is that by working out at a lower intensity “fat burning zone” the body doesn’t require getting energy quickly from carbohydrates, and therefore burns more body fat. The reality as we’ll see is different.

Let’s take two 20 minute treadmill workouts and compare.

Workout A is our lower intensity workout – walking at 3mph on the treadmill
Workout B is higher intensity – running at 6mph on the treadmill. 

According to the “fat burning zone” theory the lower intensity workout should burn more body fat right? Wrong. You can sure see why people get confused. 

What’s happened is that the time, distance traveled and total calories haven’t been taken into account.

20 Minute workoutFat CaloriesCarbohydrate CaloriesTotal Calories
3 mph Treadmill643296
6 mph Treadmill90104194

As we’ve established the body uses more calories from fat than carb (64 fat calories vs 32 carb calories) in a lower intensity workout but as you can see from the graph above, at higher intensities we burn more overall calories and more total calories from fat (64 fat calories at 3 mph vs 90 fat calories at 5 mph). 

To burn the same amount of fat calories in workout B you’d have to walk for 10 extra minutes.

Personal trainers like to use the saying: don’t workout longer, workout smarter!

In this case workout B is definitely the smarter choice! A study published in the Journal of applied physiology confirms that the exercise that maximizes fat burning is the one that expends the most total calories.

If you only have 20 minutes to workout you should be looking to burn as many calories as you can in that time to burn more calories overall and more fat calories overall. This means you workout as hard as you can in the time that you have to maximize your efforts. 

Examples of higher intensity workouts include:

  • Running rather than walking. 
  • Interval training like sprinting and stair climbing. 
  • Resistance training to increase metabolic rate.
  • Cross training, alternating cardio and resistance training

14 Best Cardio Workouts for Weight Loss, these exercises focus on maximizing calories burn both during after the workouts to trigger the afterburn effect. 

Bottom line is if your goal is weight loss, you should foucs on burning as many calories as possible. Because to lose a pound of fat you need to burn about 3,500 claories.

Overall you just want to workout smartter and budget your calorie intakes to create a calorie deficit to lose the weight.  The time you spent working out, you need to burn more total calories to be more successful in your weight loss endeavors.

Inculde a few high intensity cardio workout and resistance training sessions a week for maximum weight loss results. 

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