The Science Behind Balancing Your Diet As An Athlete

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BJJ and other martial arts are incredibly hard on the body, which you already know, and without taking care of yourself outside of the gym it’s going to get tough. Your nutrition not only affects your general quality of life, but your performance as well. If you start slacking off in the kitchen, you’ll pay for it on the mats. There are a lot of misconceptions about what to eat, when to eat, and how much to eat. No matter who you ask, you’ll get a different answer for each of these questions and it’s going to get pretty confusing.

But fear not my friends! We’re throwing out all the BS, all the bro-science, and all the anecdotes to look what the research actually says.

First, let’s go back to basics. If you think you already know the basics, just stay with me. Who knows, you might actually learn something new.


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Carbs are going to be your main source of energy, and the link between carbohydrates and athletic performance has only been strengthened throughout the years.

“But Kate!” you say, “What about ketogenic diets? My brother’s uncle’s friend completely reversed his diabetes with it and lost fifty pounds in a week!”

Be still, my friend, we’ll get there. For now, just hear me out.

Okay so we know that glycogen is converted into glucose, and this glucose is the main source of energy for muscles. Carbohydrates also require less oxygen per unit of energy than fats, and so will be a very efficient energy source for your body for up to two hours. This approximate two hour mark exists because our bodies can only store so much glycogen at once. This is also important to note because, while many believe in doing heavy carb loading before a competition, it might not help you out as much as you think it will. You’ll only be able to stuff a finite amount into your liver and muscles. After those are used up, your body will find other fuel sources to use.

It is recommended that the average athlete consume approximately 6-10 grams of carbohydrates per kilogram of bodyweight per day. (To convert your weight from pounds to kilos, simply divide by 2.2.) For example, I weigh about 63.6 kg and so would be eating between 381 and 636 grams of carbs. The amount you consume should be adjusted based on age, sex, and calorie requirements. With carbohydrates containing, on average, four calories per gram I will need to consume between 1542 and 2544 calories worth of carbs per day. Being a female, I tend towards the lower end of that range on the day-to- day.

Carbs should come from sources that are rich and complex. What do I mean when I say “rich and complex”? I mean the nutritional profile; the micronutrients as well as the macronutrients. Your carb intake should include foods such as beans (which are also a protein and high in fiber. Score!), fruits, vegetables, potatoes, minimal-ingredient wheat breads and pastas. While enjoying a treat once a week or so is fine by me, consuming much of your allotted carb intake in the form of simple sugars will only spike your blood sugar levels and make you hungrier, and screw with your insulin sensitivity. I really shouldn’t have to be telling you guys that sugar is bad in moderate to high amounts… but I just wanted to make sure we were all on the same page, okay? Okay. Moving on…


Fat is incredibly energy-dense, containing about 9 kcal/g, and should contribute about 20% of your total intake. While carbs are the go-to energy source, when the body is running long enough and hard enough, fat becomes vital. Diets that are ketogenic in nature claim accelerated fat loss, but many of the studies supporting these claims were funded by Atkin’s, Kraft, and Cattleman’s Beef (conflict of interest, anyone?). There is no evidence, as far as I could find, supporting the claims of enhanced weight loss or improved health. In fact, following a high-fat/low-carb diet can lead to certain cancers, kidney disease, osteoporosis… shall I go on? Also your brain runs almost exclusively on carbs, which is why people adopting a ketogenic diet get headaches. Just saying.

The simple truth is that HF/LC diets are nutritionally inadequate, which is part of the reason a higher-carb diet is most often recommended. That being said, fat is a very important part of your nutrition. Omega’s, mono- and – polyunsaturated fats, saturated fat and cholesterol are all important. Yes, that’s right, saturated fat and cholesterol are very important. I’m not going to get into the details here, but without them your cells can get “holes” in them and literally fall apart (yikes). Now, that’s a pretty extreme case, but you get my point. It is also necessary for your body to break down and absorb certain fat soluble vitamins such as vitamins A, D, and K.

The key with fats is eating the correct fats in the correct amounts. Breaking all of this down is more suited for the work of your doctor based on family history, current health, and nutritional needs.


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Ah yes, protein. The Holy Grail of every athlete’s diet. Some studies showed that eating a high-carb/high-protein diet could reduce overall calorie consumption and therefore reduced body fat. This is because protein is pretty good at satisfying our hunger, even though it’s almost never used for energy in healthy adults. It is important to note that while consuming a bit more protein can be good for body composition, decreasing carbs too much isn’t good for you or your athletic performance.

Consuming protein after a hard workout is shown to boost muscle repair, and some studies suggest consuming your protein immediately following exercise. While there is some speculation as to the validity of this timetable, it doesn’t hurt and so is generally safe to practice.

While protein is great, too much won’t do you any favors and can actually be detrimental to your body. Consuming more than your recommended daily allowance of protein can put strain on your kidney’s and can take away from more efficient fuel sources. Also, supplementing protein is absolutely not necessary unless prescribed by a doctor (and supplementation can be dangerous, but that’s another article). New guidelines place protein consumption recommendations at 1.2-1.7 g/kg depending on how much strength training you’re doing.


The best diet is a balanced diet, and the best calorie recommendation is for you to eat when you’re hungry and stop when you’re full. In a world laden with clickbait, it can be difficult to ascertain what’s true and what isn’t. If the idea of pouring over twenty page meta-analysis seems daunting to you don’t worry. All you really have to do is listen to your grandma: homemade is better, finish all your vegetables, and yes you can have that cookie before dinner… or half if it’s a big one.

Please note that while I do have a science background and have a degree in biology, I’m more familiar with animal and ecological health. I am not a doctor. This article is meant to help guide, not instruct. If you have any questions or concerns, please talk to your doctor. They know much better than I do.


Clifford, J., & Maloney, K. (n.d.). Nutrition for the Athlete. (Colorado State University) Retrieved from CSU Extension:
Colombani, P., Mannhart, C., & Mettler, S. (2013, January). Carbohydrates and Exercise Performance in Non-Fasted Athletes: A Systematic Review of Studies Mimicking Real-Life. Nutritional Journal. doi
Freedman, M., King, J., & Kennedy, E. (2001, March). Popular Diets: A Scientific Review. Obesity Research, 9, 1s-40s. Retrieved from
Kreider, R., Wilborn, C., Taylor, L., Campbell, B., Almada, A., Collins, R., . . . etal. (2017). ISSN Exercise and Sport Nutrition Review: Research and Recommendations. J Int Soc Sports Nutr. doi
Layman, D. (2009). Dietary Guidelines SHould Reflect New Understandings About Adult Protein Needs. Nutrition and Metabolism.
Select, N. K. (n.d.). High-Protein Diets. Retrieved from NSCA:

Engler, Laura. (2003). Effects of a Low-carbohydrate Diet on Body Composition. Nutrition Noteworthy, 6(1). Retrieved from: Escolariship






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