Antonio Cabral wrote:
Q: What do you mean by fast ?
VA: eat only 1000 calories a day if you want to lose weight. Train when hungry so the body learns to switch over toi burning fat, instead of carbos. Run at leat 14 hours after eating. If you can teach the body to shift gears this way, you can run 500 kilos (300 miles),
Dr. van Aaken's ideas about fasting have some merit with regard to ridding the body of toxins, but not for the purpose of training the body to switch over to burning fat. That is something I believed for many years. I would do all of my long runs without any breakfast believing that it was teaching my body to burn fat more efficiently. Over the years we have learned a lot more.
This article contradicts Dr. van Aaken's theory about fasting to train the body to burn fat:
Fast to Burn fat?
Source: Ellen Coleman
Q: If I want to increase my body's fat burning ability, should I skip breakfast and drink only water on workouts?
A: Ah, the "I burn more fat by not eating" myth. The short answer is no, exercising while fasting does not increase fat metabolism. Fat may contribute slightly more to the fuel mixture while fasting. However, regular exercise is beneficial for weight loss because it helps to create a calorie deficit. The fuel being burned to create this calorie deficit (fat or carbohydrate) is probably not important.
I'm going to make several comments about breakfast, exercise refueling and also about fat burning:
The main goal of breakfast is to ensure adequate blood glucose levels for the workout. After an overnight fast, liver glycogen (the source of blood glucose) is about 80% gone. Working out on empty for 45 to 60 minutes at a moderate intensity is unlikely to harm performance.
However, no breakfast may hamper performance during a long, hard workout (over an hour) workout that requires a ready supply of blood glucose.
The key to increasing fat metabolism is through endurance training, not skipping breakfast. Aerobic exercise starts the fat burning process via increases in fat burning hormones (epinephrine, norepinephrine, and growth hormone) and decreased insulin release. This hormonal milieu favors fat metabolism and occurs whether or not one has eaten breakfast.
Chronic endurance training increases fat metabolism by increasing the number and size of mitochondria (which contain the enzymes necessary to burn fat) and increasing capillary density (greater delivery of blood and oxygen which is necessary to burn fat).
For a competitive athlete, it is generally counterproductive to exercise on empty. Skipping breakfast also does not increase fat metabolism - that occurs as a benefit/adaptation of endurance training.
I also do not recommend depriving the body of fuel on long workouts to increase fat metabolism. Here's why:
1) Over the past 20 years, there has been a large amount of research demonstrating that consuming carbohydrate during exercise lasting an hour or longer enables athletes to exercise longer and/or sprint harder at the end of exercise.
2) By consuming fuel during training, the quality of the training session is better. You get more out of your training.
3) Athletes need carbohydrate to burn fat properly = fat burns in a carbohydrate flame.
4) Endurance training in and of itself increases fat metabolism and glycogen storage. As a result of endurance training, your glycogen stores are greater at the start of exercise and you go through them more slowly because you're burning more fat.
5) Consuming fuel during training decreases the stress response (your cortisol or stress hormone levels are lower) and bolsters the immune system (natural killer cell activity is higher) so you're less likely to get an infection.
Posted: October 4, 2004