CrossFit has their own nutrition advice, which has been subject to some controversy. As a sports dietitian and lover of the sport, here’s my take on CrossFit’s nutrition advice, and what CrossFit athletes need to know about nutrition.
The Demands of CrossFit
CrossFit is a combination of strength and endurance training which incorporates powerlifting, Olympic lifting as well as high-intensity interval training and gymnastics. Due to the intense nature of the sport, there is a reliance on a constant supply of energy throughout a session.
Adenosine triphosphate (ATP) is a compound that supplies energy for many bodily functions, including muscle contractions, which means that all exercise relies on ATP. The aerobic and anaerobic energy systems produce energy, or ATP. The aerobic energy system refers to the use of carbohydrates and fats to provide energy in the presence of oxygen. This system produces far more ATP than other systems, however, ATP is produced slowly, and it is not enough to maintain intense exercise. The anaerobic energy system generates ATP much more quickly, but the amount released is only sufficient for a single bout of intense exercise1 like a sprint finish or a single heavy lift.
In the context of CrossFit, the aerobic energy system will provide a majority of the energy for sessions, which highlights the importance of fuelling adequately with nutrition.
CrossFit Nutrition Advice
CrossFit has their own nutrition advice, which i’ll straight up say I don’t agree with and i’m going to tell you why…
“Eat meat and vegetables, nuts and seeds, some fruit, little starch, and no sugar. Keep intake to levels that will support exercise, but not body fat”2.
The Problem…
Not only does this statement promote a one size fits all approach, not consider training frequency and intensity or how individuals nutritional requirements and preferences may vary, but it is not conducive towards CrossFit training.
The statement also suggests a fat-phobic mentality, which likely contributes to a fear of adequate nourishment.
A study published in 2020 found that overall energy and carbohydrate intake of CrossFit athletes was insufficient to support the demands of the sport3, which is similar to the results of an earlier study which found that training may be affected due to the low carbohydrate intake promoted by the sport4.
The 2020 study3 also found that athletes were deficient in other nutrients, like calcium, folate and iron, likely attributable to the restrictive diet that is promoted by their nutrition statement. This highlights that this advice is not only problematic from a performance perspective, but in consideration of athletes general health too.
What CrossFit Athletes Need to Know…
Carbs are your friend, not the enemy
The recommendation to limit carbohydrate sources to only “little starch”2, it implies a lower intake of carbohydrates is suggested. But, a recent study found that CrossFit athletes have a higher use of carbohydrate for fuel in comparison to runners and other sports5.
Whilst both carbohydrates and fats can be used to provide energy, at high intensities, fats can’t be metabolised fast enough to produce ATP to sustain high levels of performance. A majority of a CrossFit session is performed at relatively high intensities and requires sustained strength and power, which means there is a reliance on carbohydrate to sustain the rate of ATP produced in the muscle.
The body stores carbohydrates in the form of glycogen in our liver and muscles, however, the capacity for this is limited. At full capacity, our glycogen stores can normally provide us with energy for up to 24 hours, but when we exercise, the rate at which we use glycogen is much higher. This means that during exercise, particularly high intensity exercise, glycogen stores can become depleted quicker.
When glycogen stores become depleted, power output decreases and fatigue sets in. Simply put, this could result in not being able to lift the same weight as normal, perform the same number as reps or run as quickly.
In order to prevent this, ensuring glycogen stores are ‘topped up’ ahead of a training session is of particular importance, but overall carbohydrate intake throughout the day needs to be adequate too to keep glycogen stores full.
Refuelling after a training session helps to replenish glycogen stores, which is especially important for individuals who train multiple times throughout the week. This is because glycogen stores can sometimes take more than 48 hours to fully replenish after becoming depleted6, which can affect performance in subsequent sessions.
Not only are carbohydrates important post workout for restoring glycogen stores, but also for promoting muscle recovery and repair. In the absence of sufficient carbohydrates, protein is used for energy rather than being used for the repair and growth of cells, production of hormones and enzymes, and the maintenance of our hair and nails. So, by consuming sufficient amounts of carbohydrates, it enables protein to be able to carry out its primary functions and support muscle growth and repair following sessions.
Sugar has its place in the diet too
All foods have a place in the diet, regardless of activity levels, but sugary foods can actually support performance and recovery in athletes!
Complex carbohydrates provide sustained energy as they take longer to digest. Because of this, they are not ideal to provide fast acting energy, which may be needed to boost energy levels before a training session.
Prior to a workout, simple carbohydrates (aka sugars) are ideal as they are quickly broken down which means that they provide energy fast and are unlikely to lead to digestive issues throughout a session because they are typically lower in fibre.
Following a workout, sugary carbohydrates can help to support the fast replenishment of glycogen stores, again because they are quickly digested and absorbed.
Processed foods do not need to be avoided
CrossFit’s nutrition statement hints at the idea that the diet should contain whole foods only, but nutrition is not so black and white.
Firstly, processing food does not automatically make it any less nutritious than unprocessed food, and the reality is that most foods are processed to some degree. For example, frozen vegetables are often higher in some nutrients than if they were sold as fresh, as freezing slows down the nutrient degradation.
Everything nutrition related comes down to context. In consideration of the high carbohydrate needs of CrossFit athletes, it would be hard to achieve this through whole foods alone.
Carbohydrate requirements range from 4g per kg body weight per day up to 12g depending on an athlete’s goals and training load7. To get sufficient amounts of carbohydrates from ‘fruits and vegetables’, a large volume of these foods would need to be consumed in comparison to the amount that can be obtained from foods that may be considered ‘processed’ such as fruit toast, breakfast cereal, crumpets or pasta.
and you don’t need to be a meat eater
The popularity of plant-based diets is growing, but there is still a misconception that you can’t get enough protein, or specific amino acids, on a vegetarian or vegan diet.
The good news is that you certainly can get enough protein, and all the essential amino acids on a plant-based diet… it just might take some careful consideration.
Like meat, dairy and eggs are considered ‘complete’ sources of protein, meaning that they contain all of the essential amino acids. This makes it a bit easier for vegetarians to obtain all of the essential amino acids than vegans.
Plant protein sources are typically missing, or low, in one or two essential amino acids. However, by combining different sources of plant based protein at a meal, you are likely to be able to compensate for the missing amino acids through another protein source. These are called complementary proteins. For example, beans are high in lysine but low in methionine, whereas bread is low in lysine and high in methionine, which makes beans on toast a meal that can provide all essential amino acids in comparison to eating beans or bread without another plant protein source.
Summary
Ensuring that your diet supports your CrossFit training is important for your health as well as for your performance and recovery, however, food is far more than fuel. Don’t forget to include foods you enjoy and remember that nutrition is highly individual.
CrossFit is great for fitness, for having fun and it’s known for being more than a sport and being a community. However, its nutrition advice is questionable. Please ensure to speak to a registered sports dietitian or nutritionist for advice regarding your diet. You can check out the Sport and Exercise Nutrition Register to find a qualified and experienced professional.
References:
- Gastin P. B. (2001). Energy system interaction and relative contribution during maximal exercise. Sports medicine (Auckland, N.Z.), 31(10), 725–741. https://doi.org/10.2165/00007256-200131100-00003)
- CrossFit (2002). What Is Fitness?. CrossFit Journal. Retrieved from: https://www.crossfit.com/what-is-crossfit
- Gogojewicz, A., Śliwicka, E., & Durkalec-Michalski, K. (2020). Assessment of dietary intake and nutritional status in CrossFit-trained individuals: A descriptive study. International journal of environmental research and public health, 17(13), 4772.
- 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(4), 460.
- Stanzione, Joseph R.; Brooks, George A., Bruneau, Michael L. Jr., French, Duncan N.; Nasser, Jennifer A.; Smith, Sinclair A.; Volpe, Stella L.
- Murray, B., & Rosenbloom, C. (2018). Fundamentals of glycogen metabolism for coaches and athletes. Nutrition reviews, 76(4), 243-259.
- Henselmans, M., Bjørnsen, T., Hedderman, R., & Vårvik, F. T. (2022). The Effect of Carbohydrate Intake on Strength and Resistance Training Performance: A Systematic Review. Nutrients, 14(4), 856