Old Dog, New Tricks
The interest in burning fat more efficiently during exercise is not a new trend. Endurance athletes and exercise scientists have been looking into this idea of “metabolic efficiency” for over a century. Why? Most trained runners carry ~1,500-2,000 calories of stored carbohydrates and over 80,000 calories of fat (Yes, even the string beans). If a runner can train their body to rely on this (literally) bottomless source of energy, they can take in less carbohydrate on the run, resulting in less GI distress. Plus – who does not like the idea of burning up those love handles or spare tires, instead of the carbohydrates stored in their liver? Athletes constantly strive to both look and perform better, which is why we see the resurgence of “fat burning” every decade or so.
In the last five years we have again seen a resurgence in the topic of burning fat as fuel, and with improved scientific techniques and research methods, more athletes, specifically endurance athletes, are intrigued by the thought. Some are even self-experimenting. Recent research shows that, if anyone can benefit from burning more fat and fewer carbohydrates, ultra-endurance athletes are the lucky winners. (Note: we will ALWAYS burn a combination on fat and carbohydrate during exercise, the goal is to tweak the ratio).
As a sports dietitian, I get asked about the “keto” diet and how to become “fat adapted” on a regular basis. The truth is, I don’t recommend a ketogenic diet, but not because it would not work for an endurance athlete; I actually think that teaching your body to burn more fat at a higher intensity during exercise would make you more successful as an ultra-runner, and would help you maintain a leaner body composition year-round. Of course, this would depend on the types foods you consume as part of your daily intake. I don’t recommend a ketogenic diet for a few reasons: negative long term health ramifications, nutritional imbalance, and impracticality in our culture. Not to mention, getting into and maintain ketosis is not for the faint of heart.
What, then, do I recommend?
Metabolic Efficiency Training
There is nothing wrong with carbohydrates – our brain, muscles, and blood cells need them, and they are a critical component for recovery. Rather, the problem comes with the lack of quality, and excess in quantity, in which we consume them in the United States. So when a client or athlete asks me about becoming a better fat burner, instead of directing them to adopt a ketogenic diet, I first steer them to adopt a balanced diet focused on healthy carbohydrates, paired with meal timing and a specific training plan, that produces results in four to ten weeks when done correctly. The plan is meant to be implemented during base training, when an athlete has the flexibility to train at lower intensities and prioritize fat loss versus fitness or performance. As soon as strength, interval training, and explosion become necessary pieces of the puzzle, maintaining a grain-free, lower calorie diet is inadequate for best performance, and can even be dangerous.
Metabolic Efficiency: 30% Exercise
The goal of the exercise component of metabolic efficiency training is to teach your body to use fat stores as higher intensities, when it would usually switch over to carbohydrate burning (for most individuals, this happens around 65% of your VO2max). This means you have to build an “aerobic base.” You will train fasted, at low intensities, for long hours, without taking in carbohydrates. Sound miserable? The benefit, though, is that your body adapts and finds a way to more easily access fat stores for energy.
The most important aspect of your training is frequency. You need to train at least six to seven hours weekly in heart rate zones 2-3, which is where most of your training should be during this phase anyways. The more often you train above these zones during the metabolic efficiency phase, the more likely it is that your results will be delayed. The goal length of this adaptation is four to 10 weeks, no more than about two months, and if you do it right, even shorter. So just suck it up and deal with not red-lining it for 60 days.
Metabolic Efficiency: 70% Nutrition
Nutrition plays much more a role than exercise in fat loss and metabolic efficiency. The key of this phase is to remove all grains and process/refined carbohydrates from your normal intake; this does not mean all carbohydrates. Your nutrition will include other healthy carbohydrates – vegetables, fruits, and beans – as well as lean protein, and good fats from plants and seafood. This is not a low-calorie, low-carbohydrate diet.
This is a nutrition plan with adequate calories to support muscle and tissue recovery, with a focus on manipulating intake and timing of proteins, fats, and carbohydrates around exercise. By doing so, we can control our blood sugar and insulin levels before and during exercise, enabling us to experience improved endurance and power while fueling with fewer calories and simple sugars. Processed and refined carbohydrates (even whole grains to some extent) cause an insulin spike, which reduces fat burning and increases our body’s need for carbohydrates.
What do you consume during your workout if sugar is not an option? Just water and electrolytes. You are not burning through carbohydrates, as long as you are staying under your goal intensity, so you don’t need to replenish them. If you go longer than 2-3 hours and feel the need to fuel, you can add healthy fats such as coconut oil, avocado, nut butter packs, or fat/fiber combinations like Larabars. Follow your run with a balanced meal of lean protein, healthy carbohydrates, and a small amount of good fat. And of course, adequate rehydration.
You can also add a fasted workout to your training once a week to enhance fat burning. First thing in the morning, after at least 12 hours without food, train for 90-120-minutes in zone 2-3. Refuel as above immediately after.
The Gift That Keeps on Giving
In addition to using more fat and fewer carbohydrate stores while running, there are additional benefits from becoming “metabolically efficient.” The primary benefit is improving your blood health, which includes lowering your triglycerides and bad cholesterol, controlling insulin, and stabilizing your blood sugars. This blood sugar and insulin control directly translates to decreased cortisol, increased fat loss, more stable energy levels, and fewer mood swings and food cravings. Enter a happy, lean, fit runner, who no longer deals with runner’s diarrhea, is saving money buying fewer gels and blood pressure medications and mid-afternoon cups of coffee, is sleeping well, and is setting PRs left and right.
Applying the Science
Want to know what a metabolic efficiency training plan looks like on paper? Stay tuned for March’s article, with a sample meal and exercise plan, and 10 easy steps to get you started on your own path to becoming a more efficient athlete.