Low-Carb Diets: Why or Why Not?

 

All aboard!  Another fitness bandwagon has left the station and is cruising along while building an army of “low-carb” advocates.  It is difficult to ignore the fact that almost every area of the food service industry has adjusted its marketing efforts in response to this phenomenon.  But the questions of “does it really work?” and “it is truly safe?” prevail, even amongst its most staunch supporters.  Instead of having to paddle your way through the murky waters of money–driven product promotion, I will offer some cold, hard facts surrounding low-carb diets and their potential role in weight reduction and fat loss.

            When considering any weight-loss program, one must ask oneself if their main goal is actual weight loss or a reduction in body fat.  It is reasonable to think that the two are interrelated – and they certainly can be - , but not to the degree that you might want to believe.  If your goal is to lose fat, you must provide your body with enough quality fuel without being overfueled.  This is especially true if your goal to lose fat includes exercise.  The key is not the elimination of energy packed foods, but the proper management of them.  Without adequate nutrition (including carbohydrate based foods), the body will begin to break down its own muscle tissue for energy, while conserving its own fat stores by slowing metabolism down.

            All muscle contraction is derived from ATP, which is already stored in small amounts in the muscle cells.  This ATP is available for very short bouts of physical activity, lasting up to about 15 seconds.  For the next couple of minutes, the majority of ATP is generated from the breakdown of carbohydrate (CHO), which is stored as glycogen in the muscle and liver.  After that, if the activity is continued at a sub-maximal level, fat can be broken down via slower pathways to contribute more significantly to ATP production.  So, for activities such as weight training, (where most sets last between 15 and 30 seconds), CHO is your main fuel source.  Resistance training is well documented as being a key component to any fat loss program, as you are basically trying to improve your lean mass to body fat ratio, and the best way to improve that ratio is to build muscle while burning fat.  Adequate CHO intake spares body protein (muscle) and provides the energy needed for physical activity.  Without enough CHO, your body will find it very difficult to perform any kind of resistance training or moderate to high intensity cardio exercise, as your muscle and liver glycogen stores will be virtually depleted.  Instead, your body is forced to break down its own muscle for energy, creating an internal competition for protein, and an increased strain on your kidneys to manage the resultant waste products.

            When beginning a low-carb diet (generally 100g or less of CHO/day), the depletion of glycogen stores is accompanied by a concurrent loss of water, creating a reasonably significant weight loss.  Unfortunately, most of the weight loss is water weight, and eventually muscle weight, not actual body fat.  In order to shed off unwanted body fat, one must use it as energy during physical activity, and in order to have that energy, we need to have fuel for muscular contraction, which comes primarily from CHO.  The maintenance and enhancement of muscle mass is an integral aspect of weight control, as that tissue contributes more to an increased resting metabolic rate than fat tissue does. 

            If you are serious about changing your body composition in a healthy, lasting way, the combination of adequate nutrition and regular exercise are your ingredients to long-term success.  Now that you are armed with the facts, that bandwagon may be a little less crowded or, at the very least, be filled with a better-informed army!

 

Mike Wilson is a strength and conditioning specialist with PURSUIT Training and Rehab, and can be reached at mikew@pursuittraining.com.  For a complete list of PURSUIT’s services, please visit www.pursuittraining.com.

  

                        

             

Mike Wilson

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