By Amanda Podczerwinski, MS, RD, LD, CPT
Collegiate and Professional Sports Dietitians Association (CPSDA) Member
The nutrition world is an evolving field with new information being thrown at the public daily. Many of the new fad diets affecting the general public, such as Ketogenic or Atkins diet, tend to promote a very low carbohydrate intake due to the belief that carbohydrates promote weight gain or prevent weight loss. While fad diets may temporarily work for some people, it is important to remember that not all diets are appropriate for every population. This is especially true for the athletic population. Because the brain and muscles rely solely on carbohydrates for energy, low carbohydrate intake in athletes can negatively impact athletic performance by increasing fatigue, decreasing focus, mood, and cognition, and by increasing the risk of injury. Alternatively, high carbohydrate availability has been shown to have positive effects for athletes.1 The focus needs to shift on how carbohydrates can be used to optimize performance and recovery, rather than how to limit them in the diet.
What is a carbohydrate?
In very simple terms, carbohydrates are an energy source for the body. Carbohydrates are one of the three macronutrients, alongside protein and fat. There are three main categories of carbohydrates: starch, fiber, and simple sugars. Starch is a complex carbohydrate that is found in starchy vegetables, beans and whole grains. Many of these starches contain fiber, which is essential for a healthy gut. It is recommended to consume between 25-38 grams of fiber per day. Sugar is a simple carbohydrate found naturally in foods such as fruit and milk. Simple sugars are often recommended strategically pre- and during exercise as an easily digested carbohydrate. Conversely, they can be consumed post-exercise to aid in replenishing glycogen stores, or at any time of the day in combination with other foods and food groups to meet daily needs.
Carbohydrates stored in the body are known as glycogen. The majority of stored glycogen is found in the muscles, which can store about 300-400 grams at any given time.2 Muscle glycogen can fluctuate day to day and is influenced by factors such as dietary intake and exercise. Carbohydrate is also stored as liver glycogen and blood glucose in the body.
How much do you need?
It is recommended for the general public to get at least 45-65% of their daily caloric intake from carbohydrates. However, an athlete’s needs have be described in terms of grams per kg of body weight instead of percentages. These needs range from 3-12 g/kg/day dependent upon the intensity and volume of training, as well as the goal of the athlete.2 For example, an athlete training about 60 min/day would ideally consume between 5-7g of carbohydrates/kg daily. For a 120-pound runner, they would aim to consume between 272-381 grams of carbohydrates/day. Since 1 gram of carbohydrates is equal to 4 calories, this would be approximately 1088-1524 calories a day coming from carbohydrates. Another example is a 150 lb. cyclist who trains at a moderate-high intensity for 1-3 hours/day. This athlete would aim to eat about 6-10 g of carbohydrates/kg/day, which translates to 409-681 grams of carbohydrates or 1636-2724 calories from carbohydrates daily.2 The amount consumed may be adjusted based on goals, intensity of training, and feedback from the athlete. Once we have this amount, the dietitian working with the athlete will translate that number into food examples instead of having them count grams or calories.
Fueling around workouts
As mentioned previously, the main role of carbohydrates in the body is for energy use. Having a source of carbohydrates prior to a workout can be beneficial. A simple rule of thumb is to consume the number of grams of carbohydrates/kg of body weight equal to the number of hours before a workout.2 For example, 2 hours prior to the start of exercise, an athlete should consume about 2g of carbohydrates/kg. Choosing carbohydrates that are low in fiber and paired with items lower in fat and protein will help reduce gastrointestinal distress during a workout. Great pre-workout options may include fruit, oatmeal, toast + preserves, or a granola bar.
Carbohydrate loading is a term used to describe increasing carbohydrate intake several days prior to an event that last >90 minutes in order to maximize muscle glycogen stores. The protocol is to consume between 10-12 g of carbohydrates/kg of body weight up to 48 hours preceding an event.1 For events that are shorter than 90 minutes, consuming about 7-12 g of carbohydrates/kg of body weight per day is adequate for daily carbohydrate intake.
If athletes are stating that they are experiencing fatigue towards the end of a longer and higher intense workout, it may be that they need energy throughout. Research shows that consuming carbohydrates during exercise can both improve performance and increase an athlete’s exercise capacity.2 This should be integrated into an athlete’s routine for workouts lasting more than 60 minutes. A range of 30-60 grams of carbohydrates per hour of exercise has shown to be adequate, going up to 90 grams/hour for exercise lasting more than 150 minutes.1 To give an example, 12 fluid ounces of Gatorade has about 20 grams of carbohydrates. Consuming 24 fluid ounces of this sports drink would be adequate fuel for an athlete working out for 60 minutes. Similar to pre-exercise, athletes should aim to find low fiber carbohydrates during exercise. Examples of common sources include sports drinks, fruit snacks, and apple sauce pouches.
Recovery can be just as important as fueling for a workout, as it will set an athlete up to be ready to go for the next practice or competition. The role of carbohydrates in the recovery process are to restore muscle glycogen stores utilized during exercise. Consuming carbohydrates as close to the completion of a workout will help optimize muscle recovery. It is recommended to consume 30-60 grams of carbohydrates within 30-60 minutes of exercise completion. A balanced meal should be consumed within two hours after. Adding a source of protein will also assist in repairing muscle tissue following an intense workout. A research-supported example of a balanced workout snack is chocolate milk. Chocolate milk’s 3:1 ratio of carbohydrates to protein helps refuel glycogen stores, repairs damaged muscle tissue, and replenishes fluids lost through sweat. 2
Low Carbohydrate Diets
A low carbohydrate diet is typically described as any nutrition plan in which an individual consumes less than 45% of their caloric intake from carbohydrates. There is limited, non-conclusive research that is currently available on the effects of low carbohydrate diets and athletic performance.3 Many athletes have tried cycling lower carbohydrate periods into their diet in order to promote higher adaptations to training, also known as training low. There are several different methods in which an athlete can reduce their carbohydrate availability, including performing a morning workout following an overnight fast, doing a second workout in the day with reduced muscle glycogen stores, or limiting carbohydrate intake during/after a workout. Although research has shown positive changes in skeletal muscle while training low, there is less evident information on its impact on performance.2,4 During longer periods of low carbohydrate intake, levels of training intensity and load can be compromised.2,5
There is a lot of information on the internet and in the news that could influence an individual’s dietary choices. Guiding athletes towards facts and research over the current fad can make sure that they are fueling their body properly and performing their best. Continue to encourage athletes to consume adequate amounts of all types of carbohydrate, as it is essential for optimizing athletic performance and providing sustainable energy. For more guidance or individualized help, reach out to your team dietitian or check out www.sportsrd.org for sports nutrition handouts and resources.
- Thomas TD, Erdman KA, Burke LM. Position of the Academy of Nutrition and Dietetics, Dietitians of Canada, and the American College of Sports Medicine: Nutrition and Athletic Performance. J Acad Nutr Diet. 2016;116(3). doi:10.1016/j.jand.2015.12.006
- Karpinski C, Rosenbloom CA. Sports Nutrition: A Handbook for Professionals. 6th ed. Chicago: Academy of Nutrition and Dietetics; 2017.
- Kerksick CM, Wilborn CD, Roberts MD, et al. ISSN exercise & sports nutrition review update: research & recommendations. doi:10.1186/s12970-018-0242-y
- Bartlett JD, Hawley JA, Morton JP. Carbohydrate availability and exercise training adaptation: too much of a good thing? Eur J Sport Sci. 2015;15(1):3-12. doi:10.1080/17461391.2014.920926
- Yeo WK, Paton CD, Garnham AP, Burke LM, Carey AL, Hawley JA. Skeletal muscle adaptation and performance responses to once a day versus twice every second day endurance training regimen. J Appl Physiol. 2008;105(5):1462-1470. doi:10.1152/japplphysiol.90882.2008