Over the last 20 years, it’s become popular to talk about how your body can get into a fat burning metabolism.
And so, you can exercise and run marathons functioning better on fat burning, rather than functioning on sugar burning.
At least that’s the answer supposedly. But what is the truth? Is there really a way to exercise burning fat, rather than burning sugar?
And it would be much better if we could burn fat when we exercise.
We have a lot of fat on us, at least most of us do. We have enough to run many marathons.
But the average person only has a limited amount of sugar in their body.
Sugar is stored as glycogen in the muscles and liver, and most of us have less than 24 hours worth of glycogen.
Even someone who’s quite overweight only has a limited amount of glycogen, but they have a ton of fat.
In this study, they took trained male athletes, and they gave some of them sugar during exercise, and some of them a similar tasting liquid, that did not contain sugar. In other words, it was artificially sweetened.
And they found that athletes who had the sugar during their exercise, functioned by going an extra 30%.
Imagine that: 30% longer, 30% more exercise, 30% farther.
That’s what this study showed.
In this different but more recent study, they found that indeed, when you are running, or bicycling, or doing just about anything athletic, you are burning sugar. In fact, even people in ketosis were mostly all burning sugar.
But what about cycling?
In cycling, a person will go from a high fat low carbohydrate diet, to a low fat high carbohydrate diet. The cycling is thought to increase the body’s ability to use sugar, and burn fat at the same time. In essence, it’s a way around the fact that athletes do very poorly on a low-carb diet. By cycling, the athlete can be on a low-carb diet sometime, but not all the time.
However, cycling does not help
As the study says:
high-fat, low-CHO diet strategies do not provide any benefit to the performance of prolonged endurance exercise, nor do they enhance training capacity
Even with cycling, high-fat diets don’t work. Even sometimes.
But it gets worse… Because being on a high-fat diet even for a short time can significantly limit your endurance
When people were on a high-fat diet even for a short time, even though they went back to high carbs before exercising, it severely hurt their endurance and their performance:
Therefore, the persistence of down-regulated PDH activity following fat-adaptation strategies, even in the face of CHO restoration, suggests that such dietary interventions are not advisable in situations in which sustained high-intensity efforts are required
Sorry to say, that the entire fat burning athlete idea is pure hogwash.
If you want to exercise, if you want to be active, it’s fine to eat a lot of fat. But if you care about performance and endurance, then you need plenty of carbohydrates. Otherwise, you’re not going to perform very well.