Athletes and Low Carb Diets: A Recipe for Disaster?

By Kristen Tice-Ziesmer,  MS, RD, CSSD, LD
February 21, 2014

What are low-carb diets?  They generally include the limitation of foods high in carbohydrates such as grains, rice and potatoes and encourage the consumption of high protein and high fat foods. The typical athletic diet should consist of about 50-70% of carbohydrates and diets with less than 35% of the calories coming from carbohydrates are considered low-carb. These diets are almost the complete opposite of the dietary needs for an athlete in training.  Athletes attempting to reach their peak performance energy levels need a diet full of healthy carbohydrates to fuel their intense workouts.

Low-carb diets are commonly used for the purpose of losing weight and this goal often conflicts with an athlete’s high intensity training regime.  Diet plans that attempt to completely cut out a macronutrient (carbs, fats or proteins) are most likely just a fad with faulty research backing their claims.  There is plenty of debate out there about whether low-carb diets such as Atkins, South Beach or Paleo diets actually work and if they’re even healthy, but for athletes these types of diets are known to cause a decrease in performance and energy.   

Carbohydrates are the number one source of immediate energy for athletes that participate in both endurance and weight training events.   Fat is the next source of energy for lower intensity and long duration activities and protein is rarely used as an energy source.  The storage of carbohydrates in the body is limited with only about 10g (20 calories) stored as blood glucose, 110g (400 calories) stored as liver glycogen and 400g (1500 calories) stored as muscle glycogen.  Glycogen storages are the first source of energy used for workouts and can be depleted within 20 minutes with high intensity exercise and could last up to 90 minutes with a lower intensity activity.  To replenish the limited glycogen stores for exercise, an athlete’s diet must consist of an adequate amount of carbohydrates in their everyday diet as well as before and after a workout.  Depending on the type of exercise an athlete performs a day their carbohydrate needs could range from 3-12 grams of carbohydrate per kilogram per day (g/kg/day). 

A low-carb diet couldn’t possibly provide enough glycogen storage to maintain a high intensity workout regime and in turn will result in lower energy levels and a decrease in performance.  On a low-carb diet the glycogen stores being used during high intensity exercise are quickly depleted and leads to an earlier time to exhaustion also known as hitting the wall.  In the absence of the carbohydrates needed to replenish these depleted stores, the body stays in glycogen depletion and leads to worsened future workouts.

Not only does glucose fuel your body during exercise but it is also the fuel of choice for your brain!  Low-carb diets cause physical fatigue as well as mental exhaustion which can lead to worsened moods as well as dizziness, nausea and weakness.  Carbs are also needed for fat loss and muscle gain since carbohydrates are actually stored within the muscle and when glucose is not being provided by carbohydrates, the body will break down muscle protein to convert into the glucose the body needs for energy.   Low-carb diets often cut out sources for certain vitamins and minerals such as calcium and potassium and are higher in foods with cholesterol and saturated fat which can lead to problems such as higher risks for heart disease and stroke.

What is the ultimate message here? Don’t get sucked into the low-carb diet fads thinking that they will improve your performance!  What you have been told over and over again by fellow athletes, dietitians and nutrition sources is true in that carbohydrates are an athlete’s best friend when it comes to energy.  Make sure to choose mostly whole grains as your carb sources such as brown rice, whole grain bread and rolled oats to keep those glycogen stores full!

Are you struggling to put together a fueling plan for your active lifestyle or sport? Confused on what diet, supplements and hydration practices are best for you? Sign up for Elite Nutrition & Performance’s NEW program: Athlete’s Nutrition Boot Camp and receive a personalized nutrition and hydration plan! Program starts March 4th!

For more tips and help with your own personal nutrition plan, visit www.EliteNutritionandPerformance.com   

Kristen Tice, MS, RD, CSSD, LD
Registered Sports Dietitian, Certified Personal Trainer
[email protected]
803-200-2506
www.EliteNutritionandPerformance.com