THE ENERGY SPECTRUM Part 2: Get Fast on Fat.

Achieving ultimate energy for athletes—-answering questions on ketosis, carbohydrates, and fats.

The notion of getting fast on fat is the other side of a key issue in endurance science. “Want Speed? Slow Down!” was originally written in 1982, and is about building the aerobic system through slower sub-max training as a way to achieve faster race paces.

Here is the caveat to the notion of “Want Speed? Slow Down!”

In order to accomplish this feat one must have a healthy metabolism with fat as a dominant fuel. Without this part of the equation, training slow will just result in more slow training because the aerobic system never has enough fuel (fat) to develop itself.

The most common question I receive comes from athletes who try training at lower heart rates but never get faster, or plateau after initial improvements. Without providing the aerobic system with higher amounts of fuel in the form of fat, the increased pace at the same sub-max heart rate is usually not realized.

For most people, the cause of this problem is that they are still consuming too much carbohydrate—especially the high glycemic types, which impair fat burning. (Carbohydrate addiction prevents many people from giving up these foods.)

Both sides of this issue are important—slowing down during training to build the slow-twitch-based aerobic system, and reducing carbohydrates sufficiently so more energy from fat becomes available.

Just eating a very low carbohydrate diet won’t necessarily make you faster. However, it will quickly increase the amount of energy for the slow-twitch muscle fibers, which could increase performance, sometimes significantly. (One athlete I worked with was able to run almost a minute per mile faster at the same training heart rate after two weeks of very low carbohydrate intake.)

The best way to measure improved aerobic function is with the MAF Test, described elsewhere. Basically, as more fat become available to the aerobic muscle fibers, the body can run (or bike, swim, etc.) faster at the same sub-max heart rate.

The concept is simple: increasing available energy allows the endurance muscles to perform longer and faster. This extra energy can only come from stored fat, and even the leanest athletes have significant amounts. It cannot come from sugar (glucose) because that source is very limited.

Many athletes are stuck in the slower mode because of reduced energy. And, many of those who are fast are unable to get faster for the same reason. In order to shift energy sources to increased fat burning, lifestyle must be modified—this includes eating much less carbohydrate foods and training the fat-burning aerobic system.

The Ketone Body

A bonus to burning more body fat leading to better performance includes many other healthy features. These include increasing athletic longevity and preventing injuries to name just two. What more could endurance athletes ask for?

The answer is burning even more fat. When this occurs, our metabolism significantly increases the production of ketone bodies—a group of three natural chemicals produced in the liver from fats. They are also used for energy. (Technically, they are called ketone bodies, and not ketones.)

Ketosis is the metabolic state associated with a high amount of ketone bodies in the blood. It may be an important marker, a sign that you have reached an ultimate level of fat burning. This could bring virtually unlimited energy for longer and faster training and racing, and also speed recovery each day.

Just eating a high fat diet will not accomplish high fat burning or ketosis. Only a very low carbohydrate diet (and avoiding too much protein) reduces insulin levels sufficiently to allow maximum fat burning—breaking down more stored body fat and converting it to energy.

In addition to reducing carbohydrate foods, it is necessary to add more fats to each meal to make up for the reduction of calories from the significant reduction of carbohydrates. (This is usually easy because fatty foods are the most flavorful.)

Eating more dietary fat does not mean your overall caloric intake will be higher—often, in fact, it is the same. Sometimes, calories can be reduced as individuals who burn higher levels of fat may actually require less total calories.

Measuring Ketone Bodies

The most popular way to determine whether your body is in a high state of fat burning and producing ketone bodies is through a simple dipstick test. Available in drug stores, this evaluates the presence of ketone bodies in urine. But it is only a general measure, albeit one that is adequate in most cases. To more accurately assess which ketone bodies are being produced, and in what volume, blood tests are most accurate.

More important is the fact that certain symptoms are associated with burning very high levels of fat and ketone bodies. With regular eating, one should rarely become hungry. So hunger is a common indication that fat burning is not sufficient. This is also true during training sessions. Those who require nutrient during a long run or bike are usually not burning adequate fat. Likewise for those requiring large amounts of carbohydrates during racing.

Athletes who burn large amounts of fat for fuel can eliminate or greatly reduce nutrient intake during long events.

More Fat Benefits

Many athletes want to slim down, including weight loss and reducing body fat. This can significantly lead to better economy, resulting in faster training and racing. While burning high levels of body fat are great for both health and fitness, it can do much more. It can speed recovery, reduce injuries, and improve many other aspects of both body and brain.

With more competitors rising in the age-group ranks, many also want to continue training and racing into their 60s, 70s and beyond without impairing performance. This can also be accomplished by burning high amounts of body fat.

How much fat can we burn? While it can be accurately measured during a treadmill test, one can easily make fat the predominant fuel, even during racing, reaping the benefits discussed in this article.

Ketone bodies are continually being produced in the liver of a healthy body. There is no danger in raising these levels by reducing carbohydrates. But one complication of diabetes can exist—by not properly controlling blood sugar, ketone bodies rise to dangerous levels, reducing the blood pH leading to a serious condition called ketoacidosis.

When normal physiological levels of ketone bodies are present, they are the preferred energy source for most of the body, especially in the brain, liver and heart. However, the aerobic muscles still prefer burning fat as fuel, with the presence of ketone bodies indicating a very high amount of fat available for these muscle fibers.

While certain fats are considered essential because they are potent stimulators of health, ketone bodies also have powerful therapeutic effects on the body. This and other issues are discussed in part 3 of “The Energy Spectrum.”

Join the discussion 9 Comments

  • Landon says:

    My question is regarding blood sugar levels, burning fat for fuel, and extended exercise regiments.

    My MAF zone is 147-157. I have been using the method for approximately a year, with only a few months of adapted nutritional changes suggested within the MAF method. I have started monitoring my blood sugar levels before and after training durations that are at least an hour in length. Most recently, I checked my blood sugar before a ride and it was 72 mg/dL. I didn’t feel particularly hungry. This was approximately 3 hours after a lunch of chicken, spinach, and black beans. I consume a dextrose/sucrose solution during the ride while maintaining my MAF zone. On this particular ride I consumed approximately 60oz of the solution. After a 2.5 hour ride my levels were 75 mg/dL. At the end of the ride I began to feel slightly hungry, I knew my levels were pretty low. Are my levels too low?

    In the recent months I have seen significant gains in quality of sleep, mental awareness, and training, but I am about to begin the longer training sessions this summer. My concern is being able to stay out on 5-6 hour training rides/runs with liquid energy and no solids. Will a higher blood sugar help maintain energy levels?

    • Generally, blood sugar levels are well-correlated to one’s energy level. That said, it’s always better to maintain blood sugar levels by increasing fat-burning ability (so that you burn more fat and keep the sugar at a certain level of exertion). Your question about blood sugar levels being “too low” is almost impossible to answer. 75 mg/dL is in the range of normal fasting glucose, if that’s what you mean.

      • Landon says:

        Well, if that is within fasting glucose range my assumption is that is needs to be much higher during exercise to maintain energy. Is that somewhat correct? My main concern is to keep energy level high without consuming solids. So, should I look in to supplementing more dextrose/sucrose during endurance training?

        I know the philosophy behind refined sugar consumption and sugar consumption in general. I avoid those products. My main concern is if I should be reaching an optimal blood sugar level during training. Thank you for responding.

        • Yes. There is an optimal blood sugar level. I’m not sure what it is and I don’t have the appropriate sources at hand. However, the stronger your aerobic system, the less you have to micromanage carbohydrate intake; the more your body does it for you. Kilian Jornet is a great example of this; I think that he only had like 2 energy gels during a 9 hour circumnavigation of Mt. Kilimanjaro. That said, typically most endurance athletes drink a 8-16 ounces of a 6-8% carb solution per hour, if that helps.

          I would recommend adding a touch of fats and proteins, just to help digestion, especially during very long runs.

  • Landon says:

    Thank you very much!

  • Mara Grey says:

    Any guidelines on how much protein is too much?

    • Mara:

      Let me answer with an example. During early childhood, when a human is growing at their most explosive rate, the distribution of macronutrients in their primary food (breast milk) is ~15% protein, ~56% carbohydrates and ~29% fats. Go figure.

      How much protein do you really need? if you’re an athlete you may need up to 30-35% protein. Any more than that and you’re headed towards protein toxicity.

      For example, I am an endurance athlete, and I don’t really need to go beyond 20-25% protein. When choosing foods, however, consider that greens such as spinach have 55% carbohydrates, 45% protein, and 10% fats. For comparison, a steak has 55% protein, and 45% fats. (The difference is that a steak is FAR more calorie dense than spinach.

  • Mircea Andrei Ghinea says:

    Trying to understand the ketone bodies. If they are the preferred energy source in the brain, liver and heart, then in terms of energy production where ketone body are used? in aerobic engine or anaerobic engine?

    If in breast milk there is ~15% protein, and with this amount a child has the biggest growing rate of own life, thus the biggest protein needs, then why a grown up, an athlete needs more than ~15% protein? (cause not growing anymore and all is needed is some muscle repair)

    Thank you very much!
    Best regards,
    Mircea

    • Mircea:

      Most of the guidelines for how athletes should eat come from power sports with extreme rates of muscle turnover (weightlifting, american football, etc.) they are not representative of what all athletes, let alone the rest of us, need to eat. These power athletes have very high percentages of muscle mass relative to bone and fat mass—which is not the case for soccer players or runners, for example—so they exist within a very specific nutritional context.

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