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The Key to More Muscle and Less Fat

Metabolic flexibility is the ability to switch between fuel sources, seamlessly without a change in performance.

If you are not able to burn fat, you will have trouble dropping fat and getting lean. This can also be an indicator of risk for metabolic syndrome or insulin resistance.

Being able to switch between these fuel sources is like having two jet engines with one not working. For optimal health, you want to be able to use both!

Skeletal muscle is a major player in the balance of metabolic activity. Muscle increased demand for both glycogen and lipids.

When you are metabolically flexible, your body is able to easily tap into fat storage when fasting. This is also a tactic for increasing metabolic flexibility.

In general low insulin will cause fat metabolism, while high insulin levels will lead to carb metabolism and storage. Lean people tend to be able to shift easily from fat to carb metabolism.

Are you metabolically flexible?

One way to test your metabolic flexibility is to see how you feel after having a carb meal or drink. If you feel awful, then your not using carbs well and are having trouble with  insulin. Also, if you cannot go long between meals and are bottoming out, then your having trouble tapping into fat stores for energy.  

A good way to address this is to build in a cardio workout or fasting routine.

A formula for fat loss

  1. Do not crash diet – cut calories too much as you will lose muscle mass more than fat and this will cut your metabolic power. Going to extreme carb cutting may also hinder fat loss because of the muscle mass lost. It is best to replace some carbs with quality protein.
  2. If you are weight training a couple times a week, then have a carb/protein snack before and after your sessions to help build muscle and prevent loss of lean body mass.
  3. Exercise to build stronger muscles! Exercise is the foundation of lean muscle tissue!

A loss of metabolic flexibility increases the risk for metabolic syndrome and adult onset diabetes.

On the other hand, staying metabolically flexible will allow you to use both fuel sources as needed. Going to a very low carb diet over a long period of time will decrease the body’s ability to switch back to carb burning mode, as well. The engine switch goes both ways.

Carbs are essential when doing any power or speed work. So performance is an issue when eating low carb.

Fatty acids need to be burned, as well, to help work on flipping this switch.

See my article on fatty acids for more information on why these are ALSO essential for weight loss!


Goodspaster. Metabolic Flexibility in Health and Disease, Cell Metabolism. 2017)

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