Anyone who has been in a gym within the past 25 years has seen it.
You know, that little easy-to-read chart on every piece of cardio equipment with the perfectly linear trend line showing the progression of heart rate to your exercise “stage.” Many of these visual aids like to display that when your heart rate reaches 120-150 beats/minute that you are in the “maximum fat burning” zone.
Although it is true you are burning predominantly more fat over other fuel sources like carbohydrates or protein at this time, it is not the peak of your fat burning potential. You will actually burn more fat calories at a higher intensity. However, in terms of ratios, more calories will be burnt from carbohydrates rather than fat at this higher level.
As you increase your exercise intensity, the percentage of energy provided by fat goes down, but you burn more calories per minute.
For example, when exercising at lower intensities (light walking), you may be getting 70 percent of your energy from fat but you may only be burning 5 kcal (calories) per minute. When you increase to a jog, you may be only getting 50% of your energy from fat but you may be burning 10 kcal/minute.
If you only have 20 min to get your cardio in, and you want to shed off those arm sails, step it up a notch! The only way you’re going to burn more fat calories in a set time parameter is by increasing intensity and burning more total kcal overall.