Are carbohydrates healthy for athletes?

By Nancy Clark, RD, CSSD

“I tried giving up carbs and my workouts tanked. I had no energy and felt horrible.”

Athletes’ opinions about carbohydrates range from evil to essential and its important for them to know are carbohydrates healthy for their athletic performance. Some anti-carb athletes rave about how great they feel; others complain about weakness and fatigue. Abundant research supports eating a sports diet based on grains, fruits and vegetables—the wholesome kinds of sugars and starches that feed the brain and fuel the muscles during hard exercise. If anti-carb anecdotes leave you wondering what’s best for your sports diet, keep reading.

carbohydrate meal
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Ketogenic diet and carbs

In a ketogenic diet, about 70% of the calories are from fat and only 5% from carbs. (Think drinking olive oil and eating lots of butter, not eating lots of protein) This very low carb/moderate protein diet trains the body to burn dietary- and body-fat, and produces ketones (by-products of fat metabolism) that can be used for fuel.

Speaking at the 2016 annual meeting of the Academy of Nutrition & Dietetics (AND), Jeff Volek PhD of The Ohio State University noted that a keto-diet has been used for many years in clinical situations, such as epilepsy to control seizures, obesity to lose weight, and diabetes to control blood sugar. Some athletes are now experimenting with ketosis, as a means to enhance endurance. Even the skinniest of athletes has enough body fat to support many hours of exercise. Eating a keto-diet forces the body to burn more fat. This enables an endurance athlete to consume less fuel (gels, sport drinks, gummi bears, etc.) during exercise and potentially enhance endurance IF the exercise is very low intensity (such as a 24-hour trail run). This also reduces the risk of creating intestinal distress.

An alternate way to improve performance and resolve undesired pit stops is to meet with a sports nutritionist who is a registered dietitian (RD) who can assess your diet, create a winning food strategy, and help you figure out what causes intestinal distress in the first place. You can likely resolve the issue without resorting to a tough-to-maintain keto-diet.

Why do some athletes say they feel better when they stop eating bread, cereal and other grains/carbohydrates?

When athletes rave about how much better they feel after having made any dramatic dietary change (such as cutting out grains), I ask, “What were you eating before you made this change?” Inevitably, the answer is The Standard American Diet (S.A.D.), with skipped meals, abundant fast foods, and more junk-snacks than high-quality meals. No wonder they feel better; they are eating better.

Other reasons for “feeling so much better” after giving up grains might relate to food sensitivities. When you cut out a whole food group, you eliminate a lot of foods. Likely just a few of the foods created feelings of un-wellness. An RD can help you reach the same level of “feeling great” by working with you to figure out which foods contributed to the sensitivity. Maybe cutting back on just onions and garlic could have done the job. Easier than ketosis!

Some athletes who rave about their ketogenic diet see the diet as a way to curb their “addiction” to sugar. A high fat diet curbs hunger, and simultaneously curbs cravings for sweets. An easier way to reduce sugar cravings is to prevent extreme hunger. Despite popular belief, sugar binges are unlikely due to sugar addiction but rather to the physiological effects of hunger. Again, an RD can help athletes resolve cravings for sugar without resorting to ketosis.

How are Carbohydrates used as an Energy Source for Athletes?

While there are a wide variety of sources of carbohydrates in foods, once carbohydrates enter the body, they are all broken down into glucose during the digestive process. Simple carbohydrates are easier to breakdown and will provide the quickest source of energy for the muscles. Complex carbohydrates take a little longer for the body to break down, but will also eventually be broken down into glucose. The primary difference between the two is the rate that it takes the carbohydrate to breakdown into glucose.

The most important point for athletes to understand is that “glucose is the main source of fuel for muscular activity, and the higher the exercise intensity, the greater the reliance on glucose as a fuel” (Benhardt, D., 2006). When the athlete’s body runs out of glucose, muscular fatigue will set in.

To help the body maintain glucose levels, glucose is stored in the body in a number of different ways. This is important to understand because athletes participating in high intensity or endurance sports need to eat a diet rich in carbohydrates prior to their practices/competitions in order to store as much glycogen in the muscle tissue as possible.

The largest storage for glucose is in the muscles in the form of muscle glycogen (approximately 350 grams). Glucose can also be stored in the liver in the form of liver glycogen (90 grams), and finally in the circulating blood stream (approximately 5 grams). When comparing the three storage sources, it becomes obvious that the largest organ for storing glucose is the muscles. In fact, the more muscle mass an athlete has, the more glycogen that an athlete can store.

However, there is a limit to the amount of glycogen that can be stored effectively in the muscles, liver, and bloodstream. Once a saturation point has been reached, any excess glucose is then stored as fat.

While glucose levels in the blood and stored liver glycogen are primarily fueling the central nervous system (keeping the athlete alert and focused), energy necessary to contract the muscles of the body for exercise is obtained through the breakdown of stored glycogen in the muscle. This process is known as glycolysis.

While the physiological process of glycolysis is complicated, the bottom line is that the energy necessary for an athlete’s muscles to contract originates from the food source of carbohydrates.

Best carbs for athletes

While there are many types of carbohydrates, not all are beneficial for an athlete’s body. The best foods for athletes and the type of carbs that an athlete should be consuming is based on how quickly the carbohydrate is broken down into blood glucose.

This measurement is known as the glycemic index. Foods in which the carbohydrate is quickly broken down into blood glucose have a higher glycemic index rating, while foods with higher fiber content tend to have a lower glycemic index rating.

While it is generally recommended for people to consume carbohydrates that have a low to moderate glycemic rating, there are times when an athlete might benefit from foods with a high glycemic index. Those times would be during and immediately after exercise. Examples of food that are classified as having a high glycemic index rating (greater than 70) include the following:

Baked potato…………………….85
Corn Flakes………………………..84
Pretzels…………………………….83
Instant mashed potatoes……….83
Gatorade…………………………..78
Vanilla Wafers……………………..77
French Fries……………………….75
Graham crackers………………….74
Saltine crackers…………………..74
Honey………………………………73
Bagel……………………………….72
Watermelon………………………72
White bread………………………70

Foods that fall within the moderate classification of the glycemic index rating (55-70) include the following:

Wheat bread…………………..68
Shredded Wheat……………..67
Grape Nuts……………………..67
Croissant………………………..67
Wheat thins……………………67
Life cereal………………………66
Cream of Wheat………………66
Cantaloupe……………………..65
Soda…………………………….65
Raisins……………………………64
Vanilla ice cream………………..60
Cheese Pizza…………………….60
Blueberry muffin………………..59
Power bars………………………58
Pear………………………………58
Banana……………………………56
Frosted Flakes……………………55

Examples of foods that fall within the low classification of the glycemic index rating (less than 55) include a lot of pastas and the following:

Special K…………………………54
Cheese tortellini………………..50
Linguini…………………………..50
Chocolate bar…………………..49
Carrots…………………………..49
Peas……………………………..48
Oatmeal…………………………48
Orange juice……………………46
Grapes…………………………..46
Macaroni…………………………46
Baked beans……………………44
Orange…………………………..43
Snickers bar……………………..41
Apple juice………………………40
Tomato soup……………………38
Apple……………………………..38
Chocolate milk…………………..35
Spaghetti………………………..33
Fettuccini………………………..32
Grapefruit………………………..25
Cherries…………………………..22

How many carbs daily?

The amount of carbohydrates recommended for athletes is between 55% and 65% of their total dietary intake. This has been more specifically calculated for athletes depending on the level of intensity of their sport.

Daily recovery from a moderate-duration, low intensity exercise program is recommended to be 5-7 grams of carbohydrates per kilogram (1 kg = 2.2 lbs) of body mass per day (Burke, L & Coyle, E., 2004). For example, a 155 lb athlete would need to consume 350-490 grams of carbohydrates (1,400 – 1,960 kcal) throughout the day to meet his/her energy needs.

Daily recovery from a moderate to heavy endurance exercise program is recommended to be 7 – 12 grams of carbohydrate per kilogram of body mass per day (Burke, L. & Coyle, E., 2004). This would mean consuming somewhere between 1,960 and 3,360 kilocalories of carbohydrates for a 155 lb athlete.

An athlete engaging in an extreme exercise program (4+ hours per day) is recommended to consume 10 – 12 grams of carbohydrate per kilogram of body mass per day. If the athlete is not able to maintain his/her weight, more carbohydrates would need to be consumed to match the athlete’s caloric expenditure.

Ketones vs. carbs: What does the sports nutrition science say?

A recent study in elite race walkers showed that a ketogenic diet is associated with the ability to burn very high rates of fat at high exercise intensities (1). However, the downside is that burning fat requires more oxygen. Speaking at the AND conference, exercise physiologist John Hawley PhD, Head of the Centre for Exercise & Nutrition at the Mary MacKillop Institute for Health Research (MMIHR) in Melbourne, Australia, commented that keto-athletes become less efficient and less powerful. They needed more oxygen to move at a given speed. The research indicated a sustained keto-carb diet impaired competitive performance, despite an intensified training program that improved 10-km race-walking performance by about 5% to 7% in the carbohydrate-consuming control group.

Instead of totally eliminating carbs, Hawley and his co-researcher Louise Burke, Head of Sports Nutrition at the Australian Institute of Sport and Chair in Sports Nutrition at MMIHR, suggest athletes limit carbohydrate intake around specific training sessions, so they train with low carbohydrate stores a few times a week to gain a metabolic fat-burning advantage, but still train well-fueled most of the time to support high quality workouts. To train depleted, athletes could, for example, workout hard in the evening, limit their carb intake afterwards (eat chicken and a spinach salad with lots of dressing for dinner), and then train again the next morning on empty. (Note: this is not fun, but it does boost mental toughness!) Training in a carb-depleted state in that second workout triggers beneficial metabolic adaptations that can help improve sports performance.

 

The Bottom Line

Eliminating carbs eliminates a lot of nutrients that invest in overall good health. It also limits your ability to “eat from the same pot” as your friends and family. It can strain relationships and interfere with quality of life. Yet, each competitive athlete is unique in terms of what works for his or her body and mind. One sports diet does not fit everyone and some say they are content in ketosis.

I cringe when athletes report they have eliminated carbs because they are addicted to sugar or believe that carbs are fattening. If you have a poor relationship with carbs, you want to meet with a sports dietitian who can help you find peace with grains. This professional can help you create a fueling program that you will want to enjoy for the rest of your life. To find your local sports nutritionist, use the referral network at www.SCANdpg.org.

While ketosis may seem like a fascinating nutritional adventure, in the long run, don’t you think, from time to time, you’ll want to be able to enjoy with your friends some birthday cake and/or beer?

Reference:

  1. Burke L et al. Low Carbohydrate, High Fat diet impairs exercise economy and negates the performance benefit from intensified training in elite race walkers. J Physiology, Dec 2016 (open access; read at http://ow.ly/aGAh307TFIV)