Confused By Carbs?

The low-carb diet fad has some truth in it, but it’s not for competitive athletes. Our nutrition expert serves up the skinny on carbohydrates and performance.

By Leslie Bonci

Leslie Bonci, MPH, RD, is Director of Sports Nutrition at the University of Pittsburgh Medical Center and serves as a consultant to the Pittsburgh Steelers, Pitt athletics, and several area high schools.

Coaching Management, 12.6, August 2004,

Just as athletes are starting to get the message that consuming carbohydrates is an important component of enhanced performance, the anti-carb movement has begun another full-court press. From Atkins to advertising, the anti-carb movement has many athletes doubting the standard sports nutrition recommendations.

Athletes need to separate fact from fiction. Yes, low-carb diets can lead to weight loss. Yes, low-carb diets can provide a healthy alternative for many non-athletes. But they’re not right for everyone, and athletes who follow low-carb diets will only compromise their performance.

With a glut of misinformation in the market, your athletes need to know the facts about healthy nutrition. Fact number one is that carbohydrates are a necessary part of any healthy diet. Fact number two is that carbohydrates have always been and will always be the primary energy substrate for most exercise. Fact number three is that athletes who cut carbs will pay the price with decreased speed, strength, and stamina.

Three Points
A carbohydrate is defined as a macronutrient composed of carbon (carbo-) and water (-hydrate). Carbo-hydrates are composed of saccharides (sugars) of varying length. Here are some other points athletes should consider when making dietary choices.

Point No. 1. We eat food, not just carbohydrates. Some foods are primarily carbohydrate, such as carbonated beverages. Others, such as skim milk, are a mix of carbohydrate and protein.

Point No. 2. The categorization of carbohydrates into two types, simple and complex, is much too simplistic for today’s athletes. Using these terms may persuade people to cut foods from their diet unnecessarily, making the incorrect assumption that simple carbohydrates are bad and complex carbohydrates are good.

The facts are more complicated. Some of the foods that people traditionally classify as simple carbohydrates—fruit, non-starchy vegetables, honey, maple syrup, grains (rice, corn, oats), and dairy foods such as milk and yogurt—are often a healthier choice than the foods we think of as complex carbohydrates.

In addition, some complex carbohydrates, such as sweetened cereals, have fiber removed, and may not be as nutrient-dense as simpler carbohydrates like fruit and non-starchy vegetables (green beans and broccoli, for example) which contain fiber, phytonutrients, vitamins, and minerals.

Point No. 3. Contrary to the titles of today’s top-selling diet books, your athletes need to eat a balanced diet that includes all kinds of carbohydrates.

Cutting Carbs
Low-carb diets are hot right now as the way to lose weight. According to a number of popular plans, most carbs are bad and need to be eliminated. At the same time, new low-carb products are flooding the marketplace and "success stories" abound of people who have lost weight by severely limiting or eliminating carbs.

Why do people lose weight on low-carb diets? For one thing, there are fewer food choices, which makes the diets easier to follow. Many people on low-carb diets also say they are simply not as hungry, which may be because protein makes people feel fuller, and also because low-carb diets typically allow for high fat foods, which also contribute to satiety. Decreasing carbohydrate intake also results in fluid loss, which shows up on the scale as rapid weight loss.

In addition, it’s harder to cheat on a diet that restricts carbohydrates. Many carbohydrate-containing foods are handheld and ready-to-eat, like bagels or crackers, whereas protein-containing foods tend to require preparation, utensils, and sit-down meals. Carbohydrate-containing foods are more likely to be eaten as snacks and on the go, which can lead to mindlessly consuming much more than is healthy.

Performance Factors
If low-carb diets result in weight loss, why shouldn’t athletes jump on the bandwagon and start cutting carbs? Because carbohydrate, not protein or fat, is stored in the muscles and liver as glycogen, which provides fuel for exercising muscles.

The body cannot manufacture its own carbohydrate. If carbohydrate needs are not met, the body will either break down stored fat to provide fatty acids or break down lean muscle mass to yield glucose. Most athletes would probably rather preserve muscle mass, and stored fat should be a fuel substrate for exercise, not a substitute for adequate carbohydrate intake. It is also important to realize that exercise itself depletes glycogen stores, which need to be replenished with carbohydrate, not protein or fat.

Consuming carbohydrate before exercise can help prevent hunger, delay fatigue, and provide energy during the workout. Eating carbohydrate post-exercise expedites liver and muscle glycogen resynthesis so that athletes can recover more quickly. Amazingly, there are low-carb sport bars, no-carb sports drinks, and many "energy" products with water, caffeine, and artificial sweeteners as the primary ingredients. They may taste sweet, but they are not very healthy for an active body.

How much carbohydrate is enough to fuel optimal performance? The Institute of Medicine’s Dietary Guidelines revisions call for a diet containing 45-65 percent of calories from carbohydrate and not less than 130 grams of carbohydrate per day. (By contrast, some of the low-carb diets recommend an initial carbohydrate intake of 20 grams a day—the equivalent of six ounces of orange juice, four gummy candies, or two-thirds of a cereal bar.) Some athletes may do better with a higher percent of calories from carbohydrates, whereas others may prefer a more moderate carbohydrate intake, but no athlete will improve performance when the carbohydrate content of their diet is less than 45 percent of their daily caloric intake.

To help athletes visualize the 45 to 65 percent recommendations for meal planning, have them imagine their plate divided into thirds. The protein should fit on one third, while the rest of the plate should be covered with carbohydrate-containing grains, fruits, and vegetables.

Discriminate, Don’t Eliminate
Better advice for athletes is to discriminate, not eliminate, when it comes to carbohydrates. Portions, timing, and type of carbohydrates chosen are extremely important. Instead of relying on categories that label carbohydrates as simple or complex, experts have turned to a new system for sorting carbs: the glycemic index. The glycemic index helps athletes adjust carbohydrate intake by choosing and timing carbohydrates according to the glycemic response, or effect on blood glucose and insulin levels.

Basically, eating any carbohydrate-containing food results in an increase in blood glucose levels, causing insulin to be secreted from the pancreas. The higher the blood glucose, the more insulin is released. Some scientists believe that the extent and rate at which carbohydrate-containing foods increase blood glucose and the insulin response may affect the risk for obesity, cardiovascular disease, hypertension, and Type II diabetes.

In the glycemic index system, carbohydrate-containing foods are classified according to how quickly and how much they raise blood glucose levels (i.e., their glycemic index). Foods with a lower glycemic index raise blood glucose slowly, whereas foods with a higher glycemic index raise blood glucose more rapidly. Food with a high glycemic index include pretzels, sports drinks, white bread, bagels, cold cereals, raisins, corn chips, and baked potatoes, for example. Food with a moderate glycemic index include bananas, tortillas, pita bread, 100-percent whole wheat bread, rice, pasta, citrus juices, corn, Powerbars, and grapes. Food with a low glycemic index include, milk, 100-percent bran cereal, yogurt, beans, nuts, apples, Ironman bars, and pears. The glycemic index of a food is affected by:

Particle size. Larger particles take longer to digest and slow the rise of blood glucose. That’s why regular oatmeal has less of an effect on blood glucose than instant oatmeal, which has a smaller particle size.

Soluble fiber content. Foods like oats, barley, and dried beans take longer to digest and therefore the body’s glycemic response is more gradual.

Fibrous coverings. Foods such as beans and seeds take longer to digest, lowering their glycemic index.

Acidity. Acid-containing foods such as fruit, vinegar, and pickled foods take longer to digest.

Fat content. Foods containing fat take longer to digest.

Sugar type. Fructose takes longer to digest than glucose.

From a sports perspective, foods with a higher glycemic index will produce a greater and more rapid change in insulin, resulting in enhanced glycogen replacement in the muscle, and quicker recovery times. Moderate and low glycemic index foods take longer to enter the bloodstream and may be preferred for endurance exercise to promote sustained carbohydrate availability.

I recommend that my athletes choose carbs based on the duration of their events. Athletes who have early morning practice and no time for preparing breakfast beforehand may benefit from carbs that are processed more quickly, such as sports drinks. Athletes who have long or back-to-back training sessions may feel better with a longer-lasting grain such as oatmeal, whole grain waffles, or toast before exercise.

Low-Carb Product Craze
What about choosing low-carb versions of regular foods as a way to keep carbohydrate intake at the recommended 45 to 65 percent? New low-carb foods are everywhere, from health clubs to fast food restaurants. Some of the more popular products include low-carb beer, pasta, candy, chips, muffins, pizza crust, bagels, cereal, sports drinks, and milk (the lactose is replaced by artificial sweetener and extra protein).

However, these foods are not the best choices for athletes. Some low-carb products are actually higher in calories and fat than the regular-carb versions. Others contain sugar alcohols, which can have a laxative effect. Some have an unpleasant taste and texture, and most cost significantly more money! When low-carb foods are added to a low-carb diet, variety goes up, but with it go calories, portions, and weight.

In addition, there is no industry-accepted definition for low-carb. Even more misleading, many products advertise on their labels the number of "net carbs" or "net effective carbs" in the food. The manufacturers have used net carbs as an advertising gimmick to make people believe that they are consuming fewer calories. This figure on the label is determined as follows: Net carbs = Total Carbohydrates – Fiber – Sugar Alcohols – Glycerine.

The assumption is that fiber, sugar alcohols, and glycerine do not contribute significant amounts of calories and don’t have to be counted, but this is an oversimplification. There are many factors that affect the glycemic response of a particular food, and lower net carbs doesn’t necessarily mean a lower glycemic index.

I caution my athletes to look at all of the nutrition information on the label of a food that claims to have a low number of "net carbs." Often, they’ll find that the product contains the same number of calories as regular versions of the same food. Also, although fiber is not a calorie source for the body, sugar alcohols and glycerine are, so the bottom line is that carb-free does not mean calorie-free, and low-carb foods still need to be accounted for in the daily caloric intake.

As nutrition sources, low-carb chips and muffins are not equivalent to fruits, dairy foods, and vegetables. Instead of going for low-carb gimmicks, athletes would be wise to meet their carbohydrate needs through fruit, dairy products, and grains, while limiting added sugar in desserts and snacks as well as high-fructose corn syrup present in soft drinks and sweets.

Portions Matter
While it’s essential for athletes to consume a diet high in carbohydrates, it is possible to have too much of a good thing. One reason it’s easy to overdo carbohydrates is that it’s easy to lose sight of what constitutes a portion of many carbohydrate-containing foods. There is a disconnect between true serving size and most student-athletes’ definition of a portion. I always tell my athletes, "Never eat anything bigger than your head," and as silly as that advice sounds, it reminds athletes to think about portion size.

Controlling portion size is easier said than done given the fact that a standard bottle of soda is now 20 ounces and contains two-thirds of a cup of sugar. A snack serving varies from the tiny one-ounce packages served on airplanes to the five-ounce convenience store bag. To help your student-athletes visualize appropriate serving sizes, give them the following examples:

• A two-ounce bagel is the size of a yo-yo, not a Frisbee.
• A cup of cereal is the size of a rolled up pair of sports socks, not the sports bag.
• A cup of hot cereal, pasta, or rice is the size of a tennis ball, not a basketball.
• A potato is the size of a computer mouse, not the monitor!

Fueling the Body
Despite popular diet fads, athletes will still run faster, lift more, and last longer with pasta than poultry. The body needs to be fueled, not fooled. It is the responsibility of the athletic training staff, coaches, and all others involved in the athlete’s care and well-being to encourage and recommend a varied eating plan with carbohydrate-containing foods and beverages as a major player at every meal and snack.

A version of this article appeared in Coaching Management’s sister publication, Training & Conditioning.

Sidebar: Sugar Switches
Athletes who make these substitutions at snacks and meals will get fewer carbs from sugar and more carbs from healthy fruits, grains, and vegetables.

Instead of -------------------Choose
Pretzels ---------------Trail mix with Wheat Chex, dried fruit, and some nuts
Frozen yogurt -----------Fruit flavored yogurt
Chips ---------------------Popcorn
White rice ----------------Brown rice
Lettuce salad -----------Marinated vegetables
Pasta with marinara --Higher protein or wheat pasta and add vegetables to the sauce
Sub on white bread ---Sub on whole grain
Taco salad -------------Chicken or steak fajita with vegetables or salsa in a whole wheat tortilla
Corn flakes --------------Cheerios