Fat is by far the main energy reserve of the human being, comprising up to 90% of the total energy stored. Fat is stored in the form of adipose tissue throughout the body or in the form of intramuscular triglycerides (IMTG). This refers to fat stored within operating muscles, while carbohydrates (CHO) are stored as glycogen. In addition to a brief overview, it is important to understand that exercise focus dictates what type of fuel your body will consume or use during exercise. So in general, the more intense the exercise, the more CHO burns. On the contrary, the less intense the exercise, the more fat you will burn.

The reality is that the storage of CHO, in the form of glycogen, is very small. As a result, the ability to perform high-strength exercises for a long time is also partial. You now also understand that even lean survival athletes have a large amount of fat stores, and that fat is a very opaque energy particle. Additionally, research has shown that any variation that leads to increased fat use and a reduction in precious glycogen stores generally leads to increased performance. So the only thing we can do to optimize our use of fat stores for fuel during exercise? The answer is resistance exercise.

Over time, resistance exercise results in physiological and structural changes within the muscles that are exercised to use more fat for fuel, which is highly available. Some changes within the muscles include increased capillaries and blood vessels, increased numbers of mitochondria, increased enzymes that break down fat, and an increased ability to absorb fat in working muscles for use. Therefore, several months of resistance exercise results in an increase in the total fat burned at a given running pace. Since you only have a limited source of CHO, you may have been able to run for 90 minutes before becoming fatigued and running out of stored glycogen. After several months of resistance exercise, you would have changed and adapted your body to use more stored fat and now, by running 10 minute miles, you would be burning 60% fat and 40% CHO. In this condition, you will be able to run for at least 30 more minutes or at a faster pace for the 90 minute duration.

In reality, no exact exercise will essentially increase fat burning per second. Instead, you need to choose an exercise that uses the most important muscle groups to make the most of the number of calories burned per hour, and you need to make sure that you exercise the correct amount. Exercise intensity is the key to maximizing fat burning over time.