Fear Not the Carb Loading

By Candace Chemtob, B.S. and M.S. in Human Nutrition

Carbohydrates (carbs) are one of the most misunderstood topics in nutrition. Carbohydrates have been demonized by famous doctors, like Dr. Atkins, and praised by others, like Dr. Ornish. Confused by conflicting nutrition information, it is a common practice amongst athletes to avoid carbs and load up on high protein foods. The motto, “Protein is good, carbs are bad,” is a widely held belief. When it comes to intermittent, high intensity sports, like squash, this is WRONG and may decrease your performance on the court significantly. This month’s article is going to try to make sense of all this hype and dispel some long-held fallacies about carbs.

Let’s start with the basics. There are two types of carbs, simple and complex. Simple carbs are commonly referred to as sugar. Complex carbs are a long chain of simple carbs bonded together and are commonly called starches or grains (e.g., bread, rice, pasta, etc). Food containing carbs, if chosen wisely, can be rich in vitamins, minerals, and fiber and serve as the primary source of energy in a healthy diet.

Carbs, fat and protein are the three nutrients that contain energy. The amount of energy in food is measured by a unit called the kilocalorie (Calorie). When our bodies use less energy than is consumed, it is stored. The largest quantity of stored energy is fat. The average person has over 100,000 calories stored as fat. Carbs are stored in the muscle and liver in the form of glycogen. The amount of glycogen stored in the body is a mere fraction of fat stores, reaching a maximum amount of 400 to 500g—the equivalent of 1600 to 2000 calories.

Why am I telling you all this? Athletes need to realize that muscle contractions are fueled by the release of energy from the break down of high energy bonds in a substance called ATP. Through a complex series of chemical reactions, the energy of food is converted into these high energy bonds. Carbs produce the most ATP in the shortest amount of time and are the predominant source of energy during intermittent, high intensity sports (65% VO2 max or greater).

Becoming severely fatigued on the court during a grueling match occurs when glycogen stores become depleted. Blood sugar levels will begin to drop and this signals the release of fat stores. Fat is not capable of providing ATP fast enough to support high intensity movement. Studies have shown the dramatic effect of glycogen depletion on performance. Looking at several studies, the effect of eating a high carbohydrate diet prior to training and competition can increase the time to fatigue (at 65 to 70% VO2 max) by as much as 40 to 50%!

Let’s do some numbers! Playing squash burns approximately 800 calories per hour (with variation for the intensity of your game). If you are not dieting or eating a low carb diet, you should have 800 calories of glycogen stored. However, if you do not “refuel” after each match or day, your glycogen stores will become progressively depleted and have a negative effect on the your performance.

To optimize your performance, it is recommended that your diet contain at least 50% of it’s calories from carbohydrates. In elite squash players, this level should approach 55 to 60% of total Calories with adequate energy to meet your overall needs for training. The timing of your meals, pre-, during and post- exercise will also have an impact on your glycogen stores. The general sports nutrition guidelines* are:

1. Pre-competition:
   1. 3 to 4 hours before competition: 200 to 300g carbs (Hint: Most foods have nutrition labels—get used to reading these. Please avoid “funny math” with carbs, like “net carbs” or looking at sugars vs. total carbs. Just look at total grams of carbs per serving).
   2. 1 to 2 hours before competition: Aim for 30g carbs. These foods should be high in carbs, low in fat and fiber to hasten absorption/digestion because you need them quickly. Examples: energy bars, yogurt, milk, fruits, grains, dried fruits, gels, or sports drinks.
2. During competition: The rule of thumb is that you should drink carbohydrate containing fluids during a match, if it is longer than 60 to 90 minutes. The target amount of carbs is 30 to 60g. However, more recent evidence shows that drinking a carbohydrate containing drink during a match less than 60 minutes in duration may improve performance.
3. For two hours after exercise, the muscles and liver are geared up to store glycogen. You need to take advantage of this and the recommendation is 1.0 to 1.5g carb per kg of body weight (which equals 68 to 102g carb for a 150 pound person) after your match. If you are at a tournament, you will need to prepare in advance so pack foods to bring to the court with you.

Since most of us are “carb lovers” deep down, this should be welcomed news! Enjoy your carbs and optimize your performance! Sounds like a win-win on and off the court!

*From a joint position statement of the American Dietetics Association, Dietitians of Canada, and the American College of Sports Medicine, 2009.