Ironman World Championships Hawai'i 2022

Why Athletes Need Carbohydrates

BY Dr. Rick Kattouf

Many endurance athletes are moving to a low or no carb diet in order to become more "fat efficient". Does this strategy pay off or is detrimental to your performance? Read more to find out.

In today’s world of nutrition and sport, the word “carbohydrate” is like mentioning a four-letter word. It seems that every other headline is talking about another food fad or the next latest and greatest low-carbohydrate diet. The majority of these diets and food fads suggest nutrition such as high-protein, high-fat and low-carbohydrate. For endurance athletes, the idea of burning fat rather than carbohydrates is gaining popularity.

No Fuel or Low Fuel Strategies

Many of the athletes adopting the low-carbohydrate/high-protein, high-fat diets are also adopting a “no-fuel/low-fuel” strategy during exercise and training. Many times, these athletes thought process is, “Why should I put calories in during exercise? The less I eat during exercise, the more calories and fat I will burn.” Often times individuals are drawn toward such food fads and diets because they are looking for fast weight loss. Sure, reducing carbohydrates can create fast weight loss; however, the loss is very temporary, and the weight typically goes back on quickly. This is where an athlete should ask themselves if they are looking for “change” or if they want results; meaningful and sustainable results for a lifetime. There is a big difference between these two options. A food fad or diet that brings about quick weight loss and then an even quicker weight gain did not bring about results. Rather, it simply brought about change. The body changed temporarily and then went right back. Instead, athletes should adopt a nutritious lifestyle that will produce meaningful and sustainable results for a lifetime.

The Fat Burning Myth

Many athletes avoid carbohydrates in an attempt to teach their bodies to burn fat as the major fuel source. The thinking has become that consuming carbohydrates and the ability to burn fat do not go together. The truth is that athletes can burn fat and consume carbohydrates. Always keep this statement in mind, “Fat burns in the carbohydrate flame.” Not only do carbohydrates provide energy for working muscles, they also assist in enabling fat metabolism. In short, carbohydrates need to be present in order for fat to be utilized for energy.

Avoid the Diet Carousel

Listening to the verbiage of many of these individuals that jump on the food fad and diet bandwagon there is a common theme. Say the high protein-high fat/low carbohydrate diet is called Diet-X. An individual will start Diet-X and they are super motivated. Then, within a very short period of time (sometimes as soon as one day or one week), many of these individuals will say something like the following when asked how the Diet-X is going, “Well, I am now 70/30 Diet-X.” What happened to All-In Diet-X? Well, what happened is that these individuals’ bodies began screaming for carbohydrates and thankfully these individuals listened. They are not ignoring their body, and they are feeding their body the carbohydrates that have been cut out. Of course, when their energy, performance, and recovery are still not up to their expectations the 70/30 quickly becomes 60/40, and so on and so forth.

The Mental Benefits of Carbohydrates

The need for carbohydrates is not limited to the body. Glucose from carbohydrates is the fuel the brain uses to produce the energy that moves and motivates you. According to Dr. Carol Greenwood, “Not only does a diet lacking in carbohydrates cut off the brain’s main energy supply, but a scarcity of glucose can also impede the synthesis of acetylcholine, one of the brain’s key neurotransmitters.” When she tested the memory of older adults after they ate a breakfast of mashed potatoes or barley, she found that “Eating carbohydrate foods can improve memory within an hour after ingestion in healthy elderly people with relatively poor memories.”

Vegetables Are Not Carbohydrates

In this world of high-protein diets, it seems as if there is a big misunderstanding regarding vegetables. All too often, a follower of these diets says something like, “Yes, I eat vegetables as my carbohydrate.” Well, taking a closer look at this shows that the body is not getting the necessary carbohydrates from vegetables alone. For example, one cup of broccoli has only 5.8g of carbohydrates. The bottom line is that vegetables are not carbohydrates. Sure, they may add a few grams of carbohydrates to a meal, but they are not a carbohydrate source. For example, a slice of whole grain bread has a few grams of protein, but it’s not a protein source.

Athletic Performance and Carbohydrates

When it comes to athletes and performance and their in-training fuel, once again, carbohydrates remain vitally important just as they do in everyday meals and snacks. In order to maximize and optimize performance and recovery,  athletes need to continually load and reload muscle glycogen stores. This process can not happen with a low-carbohydrate/high-protein diet. According to Ashley Chambers, M.S., and Len Kravitz, Ph.D., muscle glycogen is the primary fuel (followed by fat) used by the body during exercise. Low muscle glycogen stores result in muscle fatigue and the body’s inability to complete high-intensity exercise. The depletion of muscle glycogen is also a major contributing factor in acute muscle weakness and reduced force production. Both aerobic and anaerobic exercise decrease glycogen stores, so the need for carbohydrates is high for all types of exercise during this energy phase. Jeukendrup, Ph.D., and Michael Gleeson, Ph.D. mention that there is convincing evidence from numerous studies indicating that carbohydrate feeding during exercise of about 45 minutes or longer can improve endurance capacity and performance.

In summary, athletes looking for maximal and optimal mental acuity, performance, recovery, body composition change, and meaningful and sustainable results for a lifetime, should avoid jumping on the bandwagon of the latest food fad and diet. When it comes to nutrition, there are three key components to be spot-on with when it comes to daily nutrition:

  1. The proper eating frequency.
  2. The proper nutrient timing. When it comes to eating frequency, and nutrient timing keep it simple. Fuel up immediately upon awakening and then every 2.5-3.5 hours thereafter. Being accurate with eating frequency and nutrient timing helps assist the body in stabilizing blood sugar, insulin, and serotonin levels. This will result in high and stable energy levels all throughout the day as well as reduced if not completely eliminated food cravings.
  3. The proper macronutrient balance. At every meal/snack, seek the proper balance of carbohydrate-protein-fat. Maintaining a macronutrient balance at every meal/snack that contains 45-65% calories from carbohydrates, 15-30% calories from protein, and 15-30% calories from fat will help to stabilize blood sugar, insulin, and serotonin levels. This will help to properly load and reload muscle glycogen stores.

Proper fueling is important for endurance athletes to be able to put in the hard hours day in and day out. Don’t be afraid of carbohydrates, avoid the 70/30, 60/40 Diet-X mentality and fuel the body and brain the right way. These simple steps will help any athlete move to the next level.


Chambers, A. & Kravitz, L. (n.d.). Nutrient Timing: The New Frontier in Fitness Performance. Retrieved from

Jeukendrup, A. & Gleeson, M. (2009, December 31). Carbohydrate Intake During Exercise. In Sport Nutrition (2nd Ed.). Human Kinetics. Retrieved from

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About Dr. Rick Kattouf

Rick Kattouf II, O.D. is a 2x Best-Selling, Doctor of Optometry, Personal Trainer, Triathlon Coach, Sports Nutrition Specialist and Heart Rate Performance Specialist. Rick has been seen on ABC, NBC, CBS and Fox affiliates around the country. And Rick has been seen in the USA Today, Chicago Tribune, National Examiner,,, Runner’s World, Bicycling Magazine, Men’s Health UK, FIGHT Magazine, Florida Cycling Magazine, Pace Running Magazine,, Chicago Athlete and The Independent in the UK. Dr. Rick has personally coached individuals in 30+ states and 10+ countries. Rick can be reached at 866-966-1422

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