CrossFit athletes are some of the most exceptional physical specimens of all time. The ability to lift heavy and then perform 100 burpees may seem counterintuitive, but many CrossFit athletes do this on a regular basis and strive to improve both their strength and performance times. These individuals need to have the endurance capacity of a long-distance runner with strength-like characteristics of a powerlifter. Due to the uniqueness of the sport and the community as a whole, researchers have been interested in studying what makes these competitive athletes so extraordinary.
When discussing CrossFit, it is almost inevitable that a conversation about these individuals’ dietary preferences tends to arise. Heck, if they are willing to take their bodies through the wringer and to extreme levels physically, you would think that there would be some acknowledgement of idea dietary needs. One typical style of eating in the CrossFit community is Paleo. The Paleo-style diet was popularized by Loren Cordain in 2001 and continued to rise with the spreading of education from some of my colleagues like Robb Wolf (1). In general, the CrossFit nutrition philosophy is centered around eating “meat and vegetables, nuts and seeds, some fruit, little starch, and no sugar” (2).
CrossFit-style training has been shown to improve body composition and maximal aerobic fitness in healthy subjects. On average, over 10 weeks, body fat levels dropped about 4% in males and 3.5% in females (3). As you can imagine, the physical demand placed on the body during these workouts is extremely high. Training of such intense nature places a considerable demand on high and continuous glycogenolytic energy production (4). It is generally thought that an inadequacy in CHO intake in these individuals may compromise glycogen repletion and ultimately performance. As a result, some researchers actually suggest astronomically high levels of carbohydrate consumption, such as 8-10 grams/kg/ day for heavily-trained anaerobic athletes (5). For someone who is 175 pounds, that would equate to 640-800 grams of carbohydrates per day. While research tends to show that there is no scientific reason why anyone would ever need to consume this many carbohydrates, it’s eye opening to see those types of recommendations.
Fortunately, not everyone follows the status quo, and in fact many challenge it to help resolve unanswered questions. Recently, two incredible labs from Auburn University and James Madison University set out to look at what happens if you do the complete opposite of some of these recommendations, e.g. what happens when instead of having 20 bowls of cereal a day to hit your 800 grams, you instead had just 30-50 grams total per day and consumed a high-fat, ketogenic diet.
A driving thought behind this question was that many CrossFit athletes tend to eat Paleo and may actually enter in to some state of ketosis during their competition season with the nature of their diet combined with the intense nature of the exercise bouts. So what if we just took them and bumped their fat up a bit and dropped the carbohydrates even further to induce a state of ketosis? Would these athletes be unable to perform? Would they gain fat rapidly from consuming all of that dietary fat?
Rachel Gregory and her team from JMU recently presented on their findings of 6 weeks of a low-carbohydrate ketogenic diet implemented in athletes performing high-intensity power training as is seen in CrossFit (6). In their study, 27 individuals were randomized into either the control (their normal diet) or a low-carbohydrate ketogenic diet (ad libitum with ≤50 grams of CHO per day) and performed CrossFit workouts 4 times per week. After 6 weeks of training they found that:
The LCKD group lost an average of 3.5kg (7.7 lbs), about 3% body fat, and nearly 3kg of fat mass as measured by DXA
No significant difference in protein intake between groups!
Now what about performance? It must have plummeted, right? Wrong. When comparing the two conditions, both groups improved their times over the 6 weeks to the same degree on various tasks such as rows, squats, sit ups, pull-ups, etc.
Recently, researchers from Auburn University investigates physiological responses to ketogenic dieting in cross-trained individuals (7). Since the paper is still in review, I can tease a few of the high-level interesting findings that have been presented at a recent conference. This study was comprehensive, investigating DXA-determined body composition, ultrasound muscle thickness, resting energy expenditure, performance, and various blood health markers. Over 12 weeks, DXA-determined fat mass decreased nearly 7.5 lbs more than in the control group, with no significant differences in lean body mass or performance between the two groups.
Two different labs using a very similar population finding very similar results is a hallmark of science. For now, these recent discoveries bring new light to the idea that CrossFit and cross-training athletes may be able to simultaneously improve body composition and maintain performance while following a ketogenic diet. More studies need to investigate this further along with other strategies that may have an effect on performance, such as targeted ketogenic diets (TKD) or even exogenous ketone supplementation.
- Some research suggests that athletes training Crossfit style should consume high amounts of carbohydrates due to the energy demand of their sport.
- Paleo is a commonly used dietary strategy in the Crossfit world.
- Altering the paleo diet by reducing carbs and increasing fat could provide benefit to the Crossfit athlete.
- New research has displayed not only improved body composition but also improved performance in Crossfit athletes following a ketogenic diet.
- Wolf, R. (2010). The paleo solution. Las vegas: Victory Belt Publishing.
- Rosenbloom, C. (2014). Popular diets and athletes: Premises, promises, pros, and pitfalls of diets and what athletes should know about diets and sports performance. Nutrition Today, 49(5), 244-248.
- Smith, M. M., Sommer, A. J., Starkoff, B. E., & Devor, S. T. (2013). Crossfit-based high-intensity power training improves maximal aerobic fitness and body composition. The Journal of Strength & Conditioning Research, 27(11), 3159-3172.
- Escobar, K. A., Morales, J., & VanDusseldorp, T. A. (2016). The Effect of a Moderately Low and High Carbohydrate Intake on Crossfit Performance. International Journal of Exercise Science, 9(3), 460.
- Pendergast, D. R., Meksawan, K., Limprasertkul, A., & Fisher, N. M. (2011). Influence of exercise on nutritional requirements. European journal of applied physiology, 111(3), 379-390.
- Gregory, R. M. (2016). A LOW-CARBOHYDRATE KETOGENIC DIET COMBINED WITH 6 WEEKS OF CROSSFIT TRAINING IMPROVES BODY COMPOSITION AND PERFORMANCE.
- Roberson et al., THE PHYSIOLOGICAL EFFECTS OF 12-WEEKS OF KETOGENIC DIETING WHILE CROSS-TRAINING (2017)