Let's talk about fat burn and heart rate. This question comes up a ton for me! Now I am not a fitness expert - but this is pretty basic stuff.
In order for your body to burn off stored fat very efficiently through movement the heart rate has to be moving at a certain speed. The fat burning heart rate is the range of heartbeats per minute at which your body is using the most fat for energy. Referred to as the "fat burning zone", it is generally lower than the heart rate at your maximum capacity (also known as the "aerobic zone").
The fat burning zone is usually 50-70% of your maximum heart rate. To calculate your maximum heart rate, you can use the formula 220 minus your age. For example, if you are 30 years old, your maximum heart rate would be 220 - 30 = 190 beats per minute.
To determine your fat burning heart rate, you would then multiply your maximum heart rate by 0.50 (50%) to get the lower end of the range and by 0.70 (70%) to get the upper end...