The thought process behind carb loading the night before a match is that eating complex carbohydrates (a huge bowl of pasta or plate of mashed potatoes) will fill your muscles with with stored sugar (glycogen).

This is then supposed to provide your muscles with more fuel during your competition, allowing you to have better endurance and more energy.

From the surface, it seems to make sense and many still think this way of fueling will give them the edge in long matches. Once you dig a little deeper, the reality is carb loading actually hurts your performance on the court.

Let’s dive into the reasons why:


Your body doesn’t store glycogen efficiently, triggering excess carbs to be stored as body fat. The reality is the only thing your body is efficient at storing is fat, because it provides so much energy.

Your body stores glycogen primarily in two places: your liver and your skeletal muscles.


When your blood sugar drops, your liver releases glucose into your blood to keep your blood sugar stable. When your liver runs out of glucose, it begins to convert amino acids (muscle) into sugar. This is how low blood sugar triggers your body to consume muscle.

Here’s what happens when your blood sugar crashes:

However, when you carbohydrate load, you spike your blood sugar. This causes your body to store fat as well as glucose.

Here’s what happens when your blood sugar spikes:


The stored sugar (glycogen) in your skeletal muscle cannot be used as blood sugar, causing your body to convert amino acids (muscle) to glucose, meaning you are losing muscle.

As you see in the “where glucose is stored” illustration, your skeletal muscle lacks the enzyme glucose-6 phosphatase. Without this enzyme, your skeletal muscle cannot pass glucose into your blood, which prevents it from providing the rest of your body with needed glucose. The stored sugar in your skeletal muscle can only be used by that muscle.

During a match, your body will utilize certain muscles more than others, which means that once your more active muscles (legs, glutes, calves and arms) run out of stored sugar, they have no more fuel. This lack of fuel is the feeling you get when your legs feel extra heavy.

These energy deprived muscles are now panicking and becoming reliant on your liver for energy. Most likely, if your muscles are out of fuel, then your liver is out of its stored glucose. This triggers your liver to begin converting amino acids (muscle) into sugar in order to provide your muscles with more fuel.

This entire process will negatively affect your performance on the court, especially later in the match when every point counts.


The first two reasons will cause you to have energy crashes during your competition because the lack of available glucose in your body triggers low blood sugar. Low blood sugar is always accompanied with low energy.

Optimal recovery is created by consistent fuel during your training and your match. The facts are that your body needs to be fed consistently before, during and after your competition, which is exactly what you’ll learn in the remaining three articles in this series.

Mark Macdonald is a world renowned nutrition and fitness expert, best-selling author, television personality, international teacher and speaker, and entrepreneur who has coached everyone from celebrities to athletes to business executives to busy moms.

He is the founder of Venice Nutrition and the IBNFC: International Board of Nutrition and Fitness Coaching, author of the New York Times Bestselling books Body Confidence and Why Kids Make You Fat...and How to Get Your Body Back, as well as a featured health expert for many national media outlets.