Carb Intake, Insulin And Energy


By Jeff Volek, PhD ProSource


Exploring the Links Between Carb Intake, Energy Production, and Fat Utilization


If you ask most educated people what the primary function of dietary carbohydrate (aka carbs) is, they will tell you energy. And they would be correct; carbs provide an important source of fuel. But that’s not all they do. To truly understand how ingesting carbs affects your health and well-being you need to consider another important role of carbohydrate — that of potent regulator of metabolism. More specifically, dietary carbs have a profound impact on how the body metabolizes fat.


ATP and Carb Utilization


Adenosine tri-phosphate (ATP) is the chemical energy that fuels body processes including muscle contraction. It’s literally the energy that causes your muscle fibers to contract and produce force. At rest we are constantly breaking down and synthesizing ATP. When you exercise vigorously, ATP demands increase several-fold. Since we can’t store (nor do we eat) ATP in appreciable amounts, exercise causes an immediate need to rapidly make ATP from other energy sources. The two primary fuels our bodies draw on to do this are carbohydrate and fat. How the body chooses the proportion of carbohydrate and fat to use for fuel is complex, but one factor that has a consistent effect is the availability of carbohydrate. The more carbs that are available, the more carbs the body burns; while at the same time shutting down access to its much larger fuel reserve – fat.


Before delving deeper into the role carbs have on fat metabolism, let’s first consider how the body stores and uses fuel. Carbs are stored as glycogen mainly in skeletal muscle and to a lesser extent in liver. On average, the maximum glycogen store you can accumulate is between 400-500 grams. And since one gram of carbohydrate equals 4 kcal, you max out at about 1600-2000 kcal in your carbohydrate fuel tank. Each gram of glycogen is also stored with a couple grams of water. If you carry more muscle mass, are well trained, and eat a high-carbohydrate diet, your glycogen stores might be increased by up to another 50% or so, but the total amount of carbohydrate available in the body is still relatively low compared to available fat stores.


It’s a fact that when we digest carbs and absorb it as sugar, the body is forced to prioritize burning that sugar while simultaneously impairing access to and use of fat. Storage of sugar in the body as glycogen is limited to about enough to last one day, or just a couple hours of hard exercise. To prevent this small carb fuel tank from running dry, frequent ingestion of carbs is necessary to prevent a fuel crisis. In other words, a high carbohydrate diet locks you into a dependence on glucose as the dominant fuel for exercise.


Fat Utilization in Response to Insulin Secretion


Taking a closer look, the relationship between insulin levels and fat breakdown is not a straight line. Instead it’s a steep curve, which means that fat release decreases with just a rise in insulin such as those stimulated by most sports beverages. Looking at it from another perspective, near the bottom on the blood insulin range, decreases in insulin translate into increases in fat breakdown and fat oxidation. Thus, focusing on keeping insulin low is associated with changes in fat metabolism, favoring decreased storage and increased fat oxidation. In case you’re wondering, insulin’s effect on fat breakdown does not take days or even hours, its effect is virtually immediate.


Supplementation for the Carb-Sensitive Athlete


Why bother explaining all this metabolism? It begins to provide a basis to understand how much carbohydrate you should consume. There are some people who do fine with high-carb diets, but there are others, including some athletes, who may be struggling to lose body fat or have problems with carb fueling. If this is you, you might want to look carefully at the carb content of the supplements you’re taking pre- and post-workout and consider substituting them, in some cases, with a low-carb, high-protein drink pre- and/or post workout.


Fortunately, superior products that would fall into this category are available. A high-quality mass builder like BioQuest’s MyoZene Ultra Pro is specifically designed to fuel muscle recovery and growth with ultrahydrolyzed whey and leucine, while keeping carbs ultra low. This, in turn, makes MyoZene Ultra Pro an ideal candidate for mass-building supplementation throughout the day.


And, of course, there are pure-whey protein drinks out there which have been long associated with low carb counts and highly anabolic aminos. One such example, ProSource’s Original NytroWhey is an ultra-premium whey isolate precision-manufactured using ultra-microfiltration to preserve the most fragile protein fractions (alphalactalbumin, lactoferrin, and glycomarcopeptides) that are essential catalysts for enhancing anabolism. If you’re having trouble shedding excess fat, a logical alternative is to restrict carbs using appropriate supplementation, which will allow your body permission to access and use body fat for fuel.


Are you big, but maybe not as lean and hard as you’d like to be? What are your carb-intake strategies for addressing this situation? Let us know in the comments field below!



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