Fundamentally I have two core tenets about my running: 1) it should be fun and 2) it should allow me to eat double bacon cheeseburgers as often as I want. Given these basic precepts, it is a bit bizarre that I’ve decided to pursue Metabolic Efficiency in an attempt to improve performance.
Quick background for those new to the blog: I’ve run 10+ marathons and more recently have transitioned to ultras, including a 100k a few months ago. I’ve decided to train for a 100 miler with a goal of a ~24 hour finish – very challenging but not a reach based on existing training and performance.
Oh, and more background – I read too much and overthink everything.
So as I wandered down the wormhole of google: ultra training plans I came upon the concept of Metabolic Efficiency Training (MET). Before we go any further let’s just acknowledge that I am not a doctor, scientist or even a particularly smart person. I’ll recount what I’ve learned to the best of my ability, but go read some informative articles or listen to some good podcasts if you want to get all learned and detailed.
The basic idea is this:
Your body can store ~2,000 calories in carbohydrates in your liver and muscles. The typical human has around 80,000 calories in fat. Your body loves to burn carbs and has a really hard time burning fat. Given the choice, and especially during harder efforts (e.g., anaerobic) you will go through those 2,000 carb calories very quickly. Since your body is not very good at burning fat, you tend to bonk when you run out of carbs and maintain a hard effort.
During a marathon you can expect to burn ~3,000 calories. The prevailing paradigm is to stuff yourself full of carbs in order to top up your 2,000 calorie carb. storage and make it through the race. Carb-load, eat bars before the race, drink Gatorade and eat GUs during the run. So much of our attention around races is focused on getting enough carbs to get through the day. Now imagine a 100 miler where you are likely to burn 10,000+ calories. Since it’s impossible to get this many carbs into your body, one strategy is to train your body to burn fat instead of carbs.
Hence, Metabolic Efficiency Training.
There are two aspects to the training, the first and more complicated of which being the diet. The goal of the diet is to avoid producing insulin, which causes your body to burn carbs. This basically means that you have to follow a diabetic’s diet, eating only foods low on the glycemic index. So all starches have to go, but especially processed starches. No rice, pasta, bread, potatoes. Most fruits are out. No milk (though for some reason cheese is okay). No sugar. After a few weeks you can roll this back a bit and start eating whole grains so long as they are accompanied by fat (think whole grain corn tortillas dipped in guacamole).
So while this is not technically a low carb diet, it will obviously reduce your carb intake pretty dramatically. And that’s where training modification comes in. In order to train your body to burn fat instead of carbs, you have to reduce the intensity of training. You want to stay in the fat burning zone, which means lots of slow miles.
Dr. Phil Maffetone, the guru of this approach, has created the 180 Formula to determine how quickly you can run while staying in your fat burning zone. The basic formula is 180 – your age + a number assigned based on your fitness level. When I plug in the numbers I get 149. That means that I have to do all of my training slowly enough so that my heart rate never gets above 149.
With my cool new running watch and heart rate monitor I’m tracking this very closely and…have found out that it’s very hard for me to run at all with a heart rate below 149. I’m used to doing a pretty easy 8 minute pace on my runs, but am now running slower than 9 minute miles in order to stay in the sweet spot. This makes running a bit of a chore. It takes a lot longer and feels a lot less fun.
However, all is not lost. Running hard and getting your heart rate really high trains your body to extend the amount of time you can run anaerobically. Conversely, running aerobically over long periods increases the speed at which you can run aerobically. That means that over time I’ll be able to increase my pace and maintain a low heart rate. So maybe I’m doing 9:30 miles at a 149 heart rate today, but tomorrow I’ll be at 9:00 minute miles with the same heart rate.
When you think about it, this approach makes sense. During an ultra you spend the great majority of the race in the aerobic zone. So why are we spending so much time with anaerobic training? It makes sense that the goal of our training should be about increasing our ability to burn fat, stay in our aerobic zone and log lots and lots of slow miles. As my fitness improves I’ll be able to increase my aerobic pace and thus, over time, log lots and lots of less slow miles.
The good news is that you don’t have to do this forever. After building a base, your body will learn to burn more fat and you can slowly work more starches, etc. in to your diet without undoing all of your good work. You can also incorporate more speed and strength training into your workouts while still burning mostly fat.
My current plan is to build a base for two months using the MET training method. After that I’ll do training more specific to my actual race, including lots of hills, strength training and some speed work.
Wow, that was a long-winded explanation. True, but it’s a hard concept and if I’m going to dedicate months to this training technique, writing about it for a few hundred words doesn’t seem like such a big deal.
In my next post I’ll give you an update on how the MET method is working.