Sunday, February 8, 2015

Metabolic Flexibility: Should you stretch your metabolism???

In a world where there is plenty of confusion about whether or not carbohydrates are good or bad for you the concept of metabolic flexibility seems to have emerged. There isn't an exact definition as the idea is relatively new however if we take a look at the general theory, it's importance emerges. Metabolic flexibility is the ability of an individual's metabolism to efficiently change fuel sources both at rest and during exercise.  In this case, the primary fuel sources of interest are carbohydrates and fats. If you have taken an exercise physiology course chances are you learned the concept of fuel utilization from the classic George Brooks Textbook: Bioenergetics.  At the time fuel utilization was thought to be based on a continuum that was intensity dependent.  Looking more closely, it was thought that at rest and during low intensity exercise you burned primarily fat as a fuel source and as the intensity of exercise increased, you shifted from primarily fat burning into more carbohydrate utilization after a "crossover" point was reached. And that was basically it, bioenergetics and fuel utilization at it's finest.  Recently we are finding that this idea of fuel utilization might be more complex then we thought and might even be dynamic in nature; meaning we can "improve" it or enhance our metabolic flexibility.

Why would we want to become more metabolically flexible?
By being more metabolically flexible you would be able to switch from burning fat to carbohydrates and back again depending on the situation. This could have significant health AND performance implications.  If you're an endurance athlete, this phrase glycogen depletion may haunt your dreams as you know once you reach the point during a competition or race when you are glycogen depleted fatigue and declines in force or power output are likely to follow.  If you are able to transition to fat utilization sooner during exercise, you could ultimately spare your muscle glycogen and rely on your near endless supply of energy from fat stores.

More information found below.

How can it improve health?
Being metabolically flexible could also benefit someone from an overall health standpoint as people who can digest, absorb, store and use carbohydrates appropriately lower their risk of developing Type II diabetes or other symptoms associated with metabolic syndrome.  If you are metabolically inflexible and cannot effectively transition fuel sources, in particular if you struggle to burn fat as fuel you increase your risk for becoming insulin resistant.  The ability to use the right fuels at the right time is a survival mechanism.  For example, if your body better at utilizing fat as a fuel source in between feedings, you will be able to function better.  In addition, being more metabolically flexible will allow you to better control blood sugar levels after eating.

How do we become more metabolically flexible?
As you might expect, exercise is a great way to improve our body's capability of efficiently using and switching multiple fuel sources.  In particular, a combination of both strength training AND endurance training can improve one's metabolic flexibility.  Also, a diet high in dietary protein and fiber will help to control blood sugar levels and keep insulin levels in check.

Want more?
For more information check out this great podcast (Episode 3) from Guru Performance by Laurent Bannock MSc, CSCS, CISSN when he interviews Mike Nelson, PhD on the concept of metabolic flexibility in more detail.

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