I met this person named Peter Defty, who seems to have coined this concept called Optimized Fat Metabolism, or OFM. He introduced me into the science behind what I had already learned empirically for myself. The human body only has around 2000 calories of glycogen reserves at any given time. Unless that is replenished, it will burn quickly. The body will find every little molecule left wherever it is hiding. Blood stream, intestinal tract, kidneys, liver and muscle tissue. A body that is accustomed to supplying the brain and muscles with glycogen, will continue to want to use that source and will fatigue very rapidly when that fails. During high intensity training, such as running, the body will run out of this fuel source after about 2.5 hours or so. For long distance running, this is no bueno. Marathon runners talk about the wall, which is usually when the average runner hits this 2.5 or 3 hour mark. High performance athletes will complete a marathon in under this time frame and therefore avoid this concern, but for normal humans running out of glycogen stores is a big issue. Now we try to come up with ways to replenish this during the activity. People will load up on carbs ahead of time. Perhaps push that 2000 calorie limit to something like 2500. They will also eat sugary gel packets or drinks. The body might be able to digest some simple sugars fast enough, but usually not. Even a well trained body will not be able to restore the glycogen levels in the blood stream faster than the body burns it during high intensity exercise.
I discovered that the human body could and would actually supply the muscles with another source of energy when pushed to do so. This does not happen at the flip of a switch, it takes about 2 – 3 weeks of the body burning fat as a primary source of energy for it to get used to the idea of supplying the brain and muscles with fat as the primary source of energy. You see the human body does not discriminate, any source of energy that is burnable can and will be used to supply the mitochondria in your cells with energy, assuming it has enough electrolytes and water to aid in the transportation process. A trained body, or a body tuned to burn fat (OFM) will use fat store reserve to sustain intense training. I discovered this by accident one day. I was doing a long term fast, but I also had a commitment to run everyday for a year. So I decided to run, but just really slowly while fasting. However, the 3rd or 4th day, I discovered that suddenly I could run with energy. In fact, I could run a long time. What had happened is that my body switched to burning fat as the primary source, was trained to do so, and now I had an abundant supply. Whereas I had little to no glycogen reserves, I had massive stores of fat cells. Most people have around 15 – 20% body fat. Even a highly trained athlete will have around 10%. This means that there should be plenty of energy source to sustain muscle use and for a prolonged period of time!
So when I started to run long distances, as long as my body was in a Optimized Fat Metabolism state, then I could go on for a long period of time without fatigue from lack of energy. Muscle fatigue caused by lactic acid build up is another story. I got nervous before my first marathon and started to believe the advertisements that I needed to have glycogen packets with me, and so I did. A few weeks before the marathon I started training with sugary gels to get my stomach used to it. That worked ok, but I had a significant problem. During the actual race, I went to fast, I burned the glycogen stores faster then I could replenish them. I started feeling sick and did not want to eat the gel packs. As a consequence, I really did run out of energy about mile 21, 3 hours into the race. I bonked. I finished, but it took me almost an hour to finish the last 5 miles.
During training months previous, I had ran 30 mile distance training easily with no glycogen packets. In fact there were days that I would just run, forgetting to bring anything but water. I was in a OFM state, and I could handle it. No GI issues, no bonking, just dealing with muscle fatigue. There really is something to Mr. Defty’s idea of a body designed to burn fat during high intensity exercise.
Guy Reams
