Triathlon | UCAN Science

Metabolic Efficiency Training 101

By Dina Griffin, MS, RDN, CSSD, CISSN, METS II

Metabolic Efficiency TrainingTM (MET) is a non-diet, non-fad approach involving various nutrition and training strategies to improve the body’s ability to use its fuel sources more efficiently. Conceptualized over 12 years ago by Sport Dietitian and Exercise Physiologist Bob Seebohar, MET has evolved to provide a set of sustainable and flexible strategies that can be easily personalized around an athlete’s health and performance goals.

The roots of MET

MET has its roots in basic human physiology and metabolism principles, including the “crossover concept” which was developed in the early 20th century. Put simply and briefly, this concept laid the foundation for showing the changes in lipid (fat) and carbohydrate energy contributions as exercise intensity increases. The concept further proposed that trained athletes oxidize (or “burn”) more fat at mild to moderate exercise intensities (40-65% of VO2peak). Beyond an intensity of ~65% of VO2peak, the body would switch its predominant fuel source to carbohydrate in order to sustain the exercise intensity until glycogen stores were depleted.

While the crossover concept was largely based on the influence of endurance exercise and aerobic capacity, there was no close investigation as to the role of daily nutrition patterns. Enter MET into the picture!

As mentioned earlier, MET involves manipulations to both exercise strategies and daily and training nutrition strategies. By doing this, the body is able to “mobilize a higher amount of nearly unlimited endogenous fat stores while preserving its very limited endogenous carbohydrate stores at rest and during exercise.”

Recent research has provided evidence that athletes can far exceed the classic crossover point and are able to achieve an intensity near 87-89% of VO2peak before switching to predominant carbohydrate use. While this is highly variable between athletes, it is now more widely accepted that an athlete’s nutrition pattern can play a significant role in fuel selection during rest and exercise.

Why do we care?

Depending on leanness and body composition, athletes typically have over 60,000 calories stored as fat to mobilize for energy. In contrast, there are about 1,500-2,400 calories stored as glycogen (carbohydrate) which can quickly be depleted depending on the metabolic state of the athlete (i.e. carb burner vs. fat burner) and the intensity/duration of the exercise.

By improving fat metabolism and teaching the body to rely more on the enormous energy pool that fat provides, endurance athletes in particular can minimize their “hitting the wall” episodes. Other potential benefits of MET include improved recovery from workouts and a reduction in the need for high supplemental carbohydrate calories per hour. This in turn has benefits such as needing to carry less sports nutrition and minimizing the incidence of gastrointestinal distress during competition (bloating, abdominal cramping, vomiting, diarrhea).

How to implement MET

From a daily nutrition perspective, controlling blood sugar underlies the five food strategies that comprise MET. In its basic form, this is achieved by:

  • Adjusting amounts of protein, fat, and fiber-rich foods in meals and snacks that are appropriate to the athlete’s training cycle, health goals, and individual food preferences
  • Attention to nutrition periodization is a priority, as it is important to adjust macro- and micronutrients to ensure an athlete trains and recovers optimally.

Choosing which of the five nutrition strategies of MET to implement will depend on a number of factors. For example, athletes who work better with visuals tend to prefer the “Hand Model” and “Periodization PlatesTM” approaches, both of which avoid strict food weighing and measurement, yet feature an emphasis on food quality to stabilize blood sugar. For those who are transitioning from a very high carbohydrate diet, the “Carb Unloading” strategy allows for a gradual reduction in daily carbohydrate intake to reach an appropriate sweet spot. And for the analytical personality types, there is also a “Carb to Protein Ratio” strategy that involves a more quantitative design and assessment of meals to meet specific goals.

Training nutrition strategies vary depending on factors such as the athlete’s history of gastrointestinal distress, primary sport(s), and athletic ability (recreational versus elite/professional). A common strategy is to avoid overfeeding unnecessary calories for shorter and more aerobic-focused workouts, especially in base training. Additionally, the traditional sports nutrition guidelines of feeding 60-90 grams of simple sugars tends to be unnecessary as metabolic efficiency improves. For example, athletes tend to see matched high performance even with 25-50 grams of carbohydrate per hour. While athletes can still opt to use the traditional engineered sports nutrition, many are turning to whole food sources and novel options such as SuperStarch® to meet their energy needs and support metabolic efficiency.

While the physical training component of MET is still relevant, its role in enhancing fat metabolism is not quite as profound. The main objectives are to ensure athletes are honoring their “Zone 2” workouts and to program appropriate volume in this zone.

Who is MET for?

Truly, the principles of MET apply to any fitness enthusiast, strength/power athlete, team sport athlete, or endurance athlete. So long as there is a willingness to delve into one’s daily nutrition patterns and make necessary adjustments, much progress can be made in a relatively short amount of time.

How do you know MET is working?

Subjectively and anecdotally, metabolically efficient athletes report “positive side effects” such as improved meal satiety, steady energy levels, better sleep, body composition changes (i.e., fat loss, likely due to the positive changes in meal satiety), a reduction in sugar cravings, and quicker recovery from workouts. Interestingly, many of these benefits can also contribute to improved athletic performance!

Objectively, athletes can opt to work with a professional certified in MET who can assist in the process of proper physiological testing in a performance center. Indirect calorimetry testing (using a metabolic cart with a proper protocol) provides invaluable quantitative data for further fine-tuning of daily nutrition and training/competition nutrition strategies.

In summary, Metabolic Efficiency Training is a set of sustainable and simple nutrition and training strategies to improve fat metabolism. Athletes can reap many potential health and performance benefits with proper implementation and monitoring.

References:
Brooks, G. A., & Mercier, J. (1994). Balance of carbohydrate and lipid utilization during exercise: the “crossover” concept. J Appl Physiol (1985), 76(6), 2253-2261.

Maunder, E., Plews, D. J., & Kilding, A. E. (2018). Contextualising Maximal Fat Oxidation During Exercise: Determinants and Normative Values. Front Physiol, 9, 599.

Randell, R. K., Rollo, I., Roberts, T. J., Dalrymple, K. J., Jeukendrup, A. E., & Carter, J. M. (2017). Maximal Fat Oxidation Rates in an Athletic Population. Med Sci Sports Exerc, 49(1), 133-140.

Seebohar, B. (2014). Metabolic Efficiency Training: Teaching the Body to Burn More Fat (2nd ed.). Fuel4mance, LLC.