I have been running by the Dr. Maffetone methods for quite a while. It was not until I changed my nutritional input that I really began to see major changes in my performance. In this time I have seen my MAF pace drop by over 1:30 per mile. I have also become very fat adapted to where I can run for 3+ hours with nothing but water. I do not know how this will translate to race day, but I believe there is no way that it can hurt my efforts.
Recently I was listening to a podcast with Ultra Nutritionist Sunny Blende where she went into detail on how to become a better fat burner. She also did a prior podcast on this subject and has written an article on Metabolic Efficiency Training. She goes into enough detail to get you started down the path to become a better fat burner.
If you dive into Sunny’s material you will quickly find that you need to determine what your crossover point is. You can either be tested in a lab or you can use the well established MAF formula presented by Dr. Maffetone in this article. He also defines how to test if you are improving here. For some people this formula may be off, especially for those who have trained for many years. Here is a different view on the formula. This lines up better with where I am at right now based on my personal experimentation while running. Keep in mind these are based on a heart rate and will varying effects once Cardiac drift begins to occur. Here is another method described by Zach Bitter to determine a pace associated with the crossover point. This likely will need to be adapted to a shorter version unless you are running high mileage like Zach does.
Dr. Maffetone has also published some books on his training methods. I highly recommend the Yellow book as it goes into great detail on MAF running and nutrition. He has a newer Red book, but I have yet to read it. I believe it goes more into nutrition than the Yellow book. Dr. Maffetone has also appeared on many podcasts that are all worth your time if you are interested in his training methods. To start I would check out the archives of Trail Runner Nation, Ultra Runner Podcast, and Endurance Planet.
At the core Metabolic Efficiency Training (MET) and MAF are very similar. The both prescribe running at a sub Aerobic pace where you are burning mainly fat as fuel. They both prescribe a lower carb diet where you cut out processed foods and limit grains. One difference is that MET theorizes that your crossover point, or MAF HR will go up with training. Maffetone does not appear to prescribe to this. I do believe that this crossover point does go up as I have experienced this. Another difference is the duration of training. MAF states that you can continue to train this way until you hit a plateau with your performance. MET is prescribed for a period of time in your base training. During this period you must really watch your carb intake to maximize fat adaptation. Once the period is over you can go back to eating some grain carbs.
UPDATE: My N=1 Experience
After my period of MET training I was on travel for a week and off of that kind of nutrition. It is always hard for me to eat this way when away from home and eating out every meal with co-workers and in this case my wife. Upon returning home I continued on a low card, moderate protein, high fat diet. My focus has been on not eating inflammatory foods. So far this has been a success, but I must admit that I have a hard time on the weekends fully staying on point. I also have a theory that I run a little better when I add in one carb meal per day. What I do not know is how to maximize performance on race day. I think there are 2 options:
1) Train on very low carbs and race with moderate carbs
2) Train on some carbs and race with moderate carbs
I also have been experimenting with some intensity over the last 2 weeks and have been having a 3 carb to 1 protein recovery shake after the intense sessions. I believe this is good carb timing and allows for proper recovery on days I clearly go over the crossover point and into the glycogen stores. It may not be necessary as I am not doing these harder sessions every day and I think the science shows that recovery nutrition only speeds up recovery (need to cite this). I do not see the harm in feeding the muscles when they are most ready to be fed carbs.