|from Bob Seebohar "Metabolic Efficiency training"|
The goal of metabolic efficiency training thus becomes to move the "crossover point" to the right so that you can go faster or use more energy from fat instead of carbohydrates. What are the benefits of this other than burning body fat off the body? If we can train to burn more fat and go faster as we burn more fat, then we don't have to eat as much doing Ultras because all of us have unlimited fat stores whereas the carbohydrate stores are more limited. One of the biggest problems with Ultrarunning is the GI issues which make people vomit and unable to take in any more calories. If we can burn more fat, all you need is to drink water and run through the aid stations.
So how do we determine our crossover point? You can estimate it by using a heart rate monitor and using the formula 180-Age which is the HR to stay below while training to maximize fat burning. The most accurate way, however, is to have access to a Metabolic Cart. This is available at Human Performance Laboratories around the country (I don't think El Paso has one, nearest maybe Albuquerque) and employs a treadmill/stationary bike and a mouthpiece where all the inspired oxygen and carbon dioxide (nose is plugged). These measurements gives the amount of fat and carbohydrates that are being used. While exercising the metabolic cart will calculate the crossover point and you can get an exact measurement of the amount of effort to reach the crossover point. After training the body to burn more fat, we can go back and test to see if we have been able to move the crossover point to the right. In other words, run or cycle faster and still use more fat burning than carbohydrates.
How do we train the body to burn more fat? You accomplish this by spending more time in training at a lower intensity which stimulates the fat burning metabolic pathways and increase the efficiency. Nutritionally, you can also enhance fat burning by taking in less carbohydrates in the diet and increase fat and protein. An important factor in fat burning are the insulin spikes that result from eating a heavy carbohydrate meal and insulin inhibits fat burning. The Paleo diet, among other things, has been shown to stimulate more fat burning in a resting state precisely because you don't have these insulin spikes.
One approach which I have learned about and tried is to go out for an EASY run in the AM without eating food and maybe a little water. For nutrition doing the long runs, I have been looking into snacks that have more fat and protein with less carbohydrates to stay in the fat burning zone. Some options are Skratch Labs which make hydration solutions with less carbs.
If you have read up to this point and are interested in finding more about this topic, I would recommend the book by Bob Seebohar "Metabolic Efficiency training" or at his Website or listen to Trailrunnernation Podcast which goes into great detail and can be listened to while running very slowly by yourself because everyone else will be running faster as you do metabolic efficiency training.