You have probably heard the news that just 10 minutes of brisk walking can produce fat-burning changes that can last for up to 1 hour after exercise. This announcement made headlines but there is something that none of the news agencies picked up on. This so-called “new discovery” is nothing new!
Here is the scoop on the study:
Researchers looked at biochemical changes in the blood of people who had different levels of fitness. They studied :
- The very unfit
- Moderately fit people
- Very aerobically fit (marathon runners)
The researchers wanted to know how various chemicals in the blood changed during exercise and after exercise.
Here is what they found:
In the people who had higher levels of fitness, those metabolites involved in burning calories and burning fat, started to work significantly after only 10 minutes on the treadmill and were still working at significant levels up to 1 hour after exercise. In those who were less fit, this was not seen. In other words, the more fit we are, the better we are at burning fat during exercise and after exercise.
But, we already knew this!
As I often explain to people the number 1 rule of exercise is that fit people are better at burning fat than couch potatoes and that couch potatoes don’t burn fat very well
I say this because you and I (and everybody else) are always burning a mixture of fat and carbs.
At lower intensities of activity (and exercise), we tend to burn more fat (because it takes time to burn fat significantly).
At higher intensities of activity (and exercise), we tend to burn more carbs (because it’s a quick source of energy for the body).
These two energy systems act like gears in your car:
- At lower intensities of activity, we tend to burn more fat
- At higher intensities of activity, we tend to burn more carbs
But it is always a mixture of fat and carbs for the most part: in other words, we are never only burning fat and we are never only burning carbs – we burn a mixture of fats and carbs.
The Thing To Remember
The thing to remember is that it is the fitness level of the person that determines what this mixture is. For the very highly fit people in this study, the exercise the researchers gave them was not perceived as that difficult – so they worked more in their “fat burning gear”.
For those who were unfit, the exercise was perceived as difficult and they exhausted themselves faster (because they relied more on burning carbs which built up metabolites like lactic acid). In other words, they relied more on their carb-burning gear”.
I'm sure there was more to the study than what the news reported but the major headline was nothing new. Exercise scientists always knew that this happened.
And now you know it too!