Become A Fat-Burning Machine

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Metabolic_Efficiency_Cover_smallYour key to getting leaner and racing better may be metabolic efficiency training.

Written by: Bob Seebohar, MS, RD, CSSD, CSCS

Now is the time of the year when thoughts of dropping weight and body fat become extremely popular among runners.  But what about planning your race-day nutrition to eliminate the demon of GI distress that rears its ugly head during your races?  Attaining metabolic efficiency will have a significant impact on your body composition and GI comfort during races and will also reduce your need for simple sugars when racing.

“Efficiency” is a term that is typically associated with sport. From a nutrition perspective, being metabolically efficient simply means being able to use the proper nutrients that are stored in the body at the right times.

Metabolic Efficiency Training

Metabolic Efficiency Training (MET) comprises specific nutrition and physical training techniques that manipulate cellular processes in ways that improve the body’s ability to utilize macronutrients. The main benefit of MET is that it allows the body to more efficiently use macronutrients.

Aerobic training induces cellular changes that improve the body’s efficiency in using macronutrients, specifically fats. This is important, because fat burning is the main source of energy when the exercise intensity is low.  Because the muscle stores of glycogen (carbohydrate-based fuel) can deplete rather quickly (after two to three hours of moderately intense exercise) and supplemental carbohydrates (e.g. sports drinks) cannot provide adequate energy for longer-distance training due to the GI distress they cause or the inconvenience of transport, it is beneficial to teach the body to become more metabolically efficient in using fats as an energy source.  These metabolic changes can typically happen in as little time as two weeks with the proper eating and training program.

The Crossover Concept

The crossover concept is a physiological term that describes the relationship of fat and carbohydrate oxidation to intensity of exercise. As exercise intensity increases, the body prefers to use carbohydrate for energy.  The crossover point is the intensity where fat and carbohydrate intersect with the energy from fat decreasing and the energy from carbohydrate increasing. The crossover point, or what I term “metabolic efficiency point”, can be manipulated with proper aerobic training, but only if intensity is maintained at lower levels.  Training at higher intensities will surely improve power and speed but it will not improve fat metabolism during training.  A runner who is more aerobically conditioned can use more fat as energy at higher intensities and this can provide a glycogen-sparing effect.

The metabolic efficiency point can be further manipulated through nutrition.  Eating a higher carbohydrate diet will lead to an increase in carbohydrate oxidation. While the benefits of eating a higher-carbohydrate diet are certainly justified during certain times of the year when the training load is high, this type of eating can work to a runner’s disadvantage during lower-volume and -intensity cycles.

Eating and therefore oxidizing more carbohydrates decreases the body’s ability to oxidize fat at higher intensities; therefore, to properly teach the body to utilize fats more efficiently, carbohydrate intake should be more balanced with lean protein and healthy fats. This is not a recommendation to follow a low-carbohydrate diet. The goal is to balance macronutrient intake so proper metabolic changes can happen.

The good news is that any athlete can accomplish these metabolic changes in a short amount of time. There are no special tools or devices that you need. The following three steps will help in your quest to become more metabolically efficient and use more of your fat stores as energy.

1. Adopt a nutritional paradigm shift.  As you approach your daily food selection, prioritize your meals and snacks.  First on your plate should be a source of lean protein and healthy, omega-3-rich fat.  Second up is a healthy portion of fruits and/or vegetables.  Then, save just a little room for those whole grains and healthier starches if you decide you need them at this point in your training cycle.

2. Use the “out of sight, out of mind” concept.  Nutrition supplements that are high in simple sugars such as sports drinks, energy bars, gels and chews will inhibit your progress toward metabolic efficiency. Focus on eating good meals as I described above and save the nutrition supplements for when you really need them.  Remember, you are trying to teach your body to use its fat stores more efficiently and these products will just interfere with that goal at this time.

3. Follow the 90/10 rule.  Stay on track with these steps 90 percent of the time and allow yourself to “miss” the other 10 percent of the time.  Remember, you are human and life happens.  Don’t stress out if you have the occasional “miss”.  Be gentle with yourself and allow some room to deviate.

This is the best time of the year to implement a metabolic efficiency plan.  Focus on good aerobic training with some nutritional shifts and you will be on the road to using more of your internal fat stores as energy.


For more information about this topic, refer to Bob’s newly published book Metabolic Efficiency Training: Teaching the Body to Use More Fat.

Bob Seebohar, MS, RD, CSSD, CSCS, is one of the foremost experts on sports nutrition for endurance athletes. He was previously the Director of Sports Nutrition at the University of Florida and most recently a Sport Dietitian for the US Olympic Committee.  Contact him at

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