The order in which your macronutrients are used

Many Americans on low carbohydrate believe that once they limit their carbohydrates their fat stores will be used as energy and not their protein stores. This is true in some instances, however many factors determine the order in which your body uses macronutrients for fuel. Understanding metabolism will ease the confusion.

At rest your body mainly uses fat to provide energy. However, do not plan on sitting all day to burn those last few pound off for summer. During aerobic exercise fat is the primary fuel source used when the intensity is low. As the intensity increases so does the use of carbohydrates. During weight lifting carbohydrates, creatine, and ATP all provide your body with the needed energy. Now to bring the focus back to the low carb diet belief it is true that carbohydrates are the primary fuel source because they can be converted into glucose the fastest. Fat stores take longer to be converted into energy. Protein stores require the most oxygen in order to be broken down for energy. This is why performing aerobics at a low intensity is best for utilizing fat stores. Protein can be used for fuel in gluconeogenesis in order to produce glucose when carbohydrates are not available. This will cause muscle breakdown, which is why protein are usually used up last. When carbohydrates are restricted from the diet fat stores will be used for the primary energy source, however be aware that proteins will be used more frequently for energy when this occurs, thus running the risk of loosing lean muscle mass. When your lean muscle mass is reduced so is your caloric expenditure and weight loss goals. When on a low carbohydrate diet it is important to understand how to perform your workouts in order to prevent muscle breakdown and increase fatty acid utilization.  

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