Over the last couple of weeks, I have been talking about increasing the ability to burn fat as a source of energy. Basically what it comes down to is reducing the amount of high carb foods you eat, so the body is not constantly trying to reduce the sugar load on the body. Also in enabling the body to oxidize fat, we are reducing our fat stores, great for some of us struggling to lose those extra inches off the waist, and increasing our endurance. If we burn more fat for energy, we are burning less carbs and rely less on carrying fuel on the long runs.
But there was one technique to boost your fat oxidation rate that blows all the other methods out of the water. This method has allowed many runners to run marathons and some ultras without fuelling at all. Sound interesting? Well the method to boost your fat burning metabolism is called ketosis. Now some of you who know diabetics may be freaking out at this term as diabetics can go into a state called keto acidosis which is quite a dangerous state to be in. But it is like comparing a paper cut to losing a limb. Sure they are both cuts, but only one is life threatening.
Ketosis is basically something the human race has used to survive all through the hunter gatherer phase of evolution until farming was invented. You see, in nature, high carb foods are not readily available all year round, so when they are readily available, we burn glycogen/sugar for energy as they are in abundance. But when winter comes and the crops stop growing, we need some way for our bodies to get its energy. This is when ketosis kicks in.
To put it simply, it’s a complex chemical process where we produce acetoacetate to be converted into beta hydroxybutyrate (BOHB) which breaks down the fat molecules in our body to be burnt as energy. The only way to achieve this state is purely by carbohydrate restriction replaced by more fat. The body need roughly 130 grams of carbohydrate every day to function on a basic level (ie fuelling the main organs like the heart and brain) and anything under this amount needs to be produced by other means.
Going into ketosis is not something that happens overnight. There is an adaption phase which varies for the individual, although 2 weeks is considered long enough for the average person to “adapt” to it. During this time, endurance and energy levels can and most often reduce. There have been many studies to see if fat can be used as a reliable energy source, but most are flawed. Most of them study people who have been on a high fat diet for 5 to 10 days, where they concluded that endurance reduced on a high fat diet. But there is a couple of researchers by the names of Jeff Volek (PhD) and Steve Phinney who have gone further than most to study these effects.
In one study they recruited 5 bike racers who were quite lean and very fit. They were asked to ride a stationary bike at 60% of peak aerobic power until exhaustion while only consuming water (no outside sources of energy). While on the high carb diet, they averaged 147 minutes. After a 4 week adaption to a ketogenic diet where they ate 15% of their calories from protein, 80% from fat and minimal amounts of carbohydrate (about 10 grams per day), they were again tested. Peak power output was unchanged, and in the endurance test they managed 151 minutes. A slight improvement, but with further adaption, it is believed they can still improve.
The main difference was in the second test, the muscle glycogen was half of the first test and they only oxidized half of that. Meaning they only used a ¼ of the glycogen compared to the previous test. The rest came directly from their fat stores, even though they were relatively low in fat stores to start with.
We don’t need to go to the extremes that these cyclist went through to get into the fat burning zone. Their diet was extreme, even by ketogenic standards. But eating 50 grams of carbs per day for the average Joe and 70-80 grams per day for athletes is readily accepted as sufficient. Protein intake should be around 1-1.5 gram per day per Kg of lean body mass and the remainder from fats. It may sound quite gross to be eating this much fat, but actually becomes quite tolerable after a short time provide the right fats are chosen.
The advantages are many and varied for us athletes, but to go into them all would require another full blog from me. If you are interested into seeing how any of the diets I have mentioned over the past few weeks work, feel free to message me with your questions.