Why Training Type Should Shape Your Nutrition Strategy
Let’s get one thing straight, your body isn’t a machine that runs on the same settings day in day out. The way you train, whether that’s long-distance running, Olympic lifting, CrossFit or a steady programme of strength and hypertrophy, places unique demands on your muscles, hormones, metabolism and nervous system. And those demands can’t all be met with the same plate of food.
Yet that’s exactly what many people do. They follow one-size-fits-all nutrition advice, regardless of how they train. Worse still, some fitness fads have managed to convince entire communities to follow diets that actually compromise performance.
If you’re someone who coaches others through their nutrition or you’re thinking of expanding your knowledge with nutrition coach courses, understanding how nutrition needs to adapt to different training types is absolutely essential.
Fuelling Is Specific to the Stimulus
Think of energy systems like gears in a car. Endurance training, such as running or cycling, tends to cruise in the aerobic gear, which is steady, sustained energy, mostly from carbohydrates and fat. In contrast, heavy lifting or sprinting relies more on the phosphagen system. This is the fast system for powerful bursts that tap into stored ATP and creatine phosphate. High-intensity functional training, like CrossFit, flips through the gears so fast it can feel like being stuck in traffic on a manual transmission.
The point? You can’t fuel all of these systems the same way. And if you try, performance and recovery are going to take a hit.
The Ultimate Mixed Energy System Challenge
A brilliant (and brutal) example of this is CrossFit. It’s a constantly varied mix of aerobic and anaerobic training. It’s like Olympic lifts followed by rowing intervals, box jumps and handstand push-ups. One day might focus on max effort strength, the next could be a 20-minute “As Many Rounds As Possible” (AMRAP) grinder that leaves you in a heap on the floor.
This variety makes CrossFit both effective and notoriously hard to fuel properly. Which is why a new study from Martinho et al. (2025) is so useful. Titled “Nutrition in CrossFit® – scientific evidence and practical perspectives: a systematic scoping review”, the paper pulled together 49 studies on the dietary habits, macronutrient intake and supplement use of CrossFit athletes. And the findings were really quite interesting.
Let’s start with energy intake. Across the board, CrossFit participants, female participants in particular, were eating less than they needed. The average daily intake was around 2,247 kcal, with women coming in even lower at 1,746 kcal/day. Compare that to estimated energy expenditure of 2,598 kcal for females and 2,828 kcal for males, and you’re looking at a daily deficit of 500–800 calories. That’s a fast track to under-recovery.
And carbohydrates, the one macronutrient that’s absolutely critical for high-intensity training? Most participants weren’t getting anywhere near enough. The average intake was 3.6 g/kg/day. But guidelines for athletes in demanding sports like CrossFit suggest 5–7 g/kg/day at a minimum. Worse still, this number appears to be trending downwards over time, likely due to the popularity of diets like Paleo or Zone which restrict carbs to 30–40% of total energy intake.
Interestingly, protein intake was more on point. Both men and women averaged around 1.7 g/kg/day, which aligns well with recommendations for strength athletes (1.6–2.2 g/kg/day). So while recovery may be partially supported through protein intake, the missing glycogen from low-carb intake means energy levels as well as workout performance, are taking a hit.
But What About Supplements?
The study also looked at what supplements CrossFitters are using and whether they’re working.
Unsurprisingly, protein powder and creatine topped the list. Around 72% of participants used supplements regularly, with creatine and whey being the go-to options. This is smart. Creatine has decades of research backing its effectiveness for improving strength, power and short-duration performance, all of which are key in CrossFit. It also supports muscle recovery and adaptation over time.
Whey protein, meanwhile, is rapidly digestible and rich in leucine, which is great for stimulating muscle protein synthesis after training.
Caffeine was also popular. Studies in the review explored its effects on performance. At a moderate dose of 6 mg/kg taken 60–70 minutes before training, caffeine had a small effect on performance. Although not statistically significant, it’s something that’s possibly meaningful for some. It’s worth noting that individual tolerance, habitual use and even genetic factors all play a role here.
However, other supplements including carbohydrate drinks consumed during workouts, didn’t show clear benefits. This may be because many CrossFit workouts are too short to require intra-session fuelling. Glycogen depletion typically becomes a concern during longer sessions or multiple sessions in a day. So the timing and context of supplementation still matter.
CrossFit vs. Endurance Training
To put this in context, let’s compare CrossFit to endurance training, like long-distance running or cycling.
Endurance athletes have very well-established guidelines for fuelling. This is primarily due to the fact they train at lower intensities over longer durations, and the link between carbohydrate availability and performance is crystal clear. Recommendations often call for 6–12 g/kg/day of carbohydrate, depending on volume, along with strategic fuelling during exercise (30–90g per hour) to delay fatigue and maintain performance.
Endurance athletes also tend to periodise their nutrition according to training load and race demands. They’re encouraged to “train low, compete high” when it comes to carbohydrate availability, sometimes manipulating carb intake to encourage fat oxidation adaptations.
In contrast, CrossFit’s variability makes it harder to plan around. One session might not deplete glycogen much at all, while another, like the infamous “Murph”, might demand every last gram. Unfortunately, many CrossFitters under-fuel consistently, which leads to under-recovery, fatigue and eventually injury or stagnation.
Practical Takeaways for Coaches and Athletes
So, what does this mean for fitness professionals?
First, take the training stimulus into account. Nutrition isn’t just about what’s “healthy”. It’s about what supports the specific demands of your training. If you or your clients are doing daily CrossFit workouts, especially with a mix of lifting and metcons, you need to fuel accordingly.
That means:
- Prioritising carbohydrates. Aim for 5–7 g/kg/day during moderate-to-high training loads.
- Maintaining adequate protein. Stick with 1.6–2.2 g/kg/day, ideally spread across the day.
- Being smart with supplements. Creatine and whey are well supported. Caffeine might help, but individual response matters.
- Monitoring energy availability. Use food logs or apps to check for chronic under-eating – especially common in female athletes.
- Considering nutrition periodisation. Heavy training week? Carb up. Recovery week? Adjust intake accordingly.
Wrapping Up
Different workouts demand different fuel. Endurance athletes need sustained energy and intra-session fuelling. Strength athletes need enough protein and total calories to support adaptation. CrossFitters, with their high intensity and daily variability, need a smart balance of both.
But across all these approaches, one truth remains; under-fuelling will hold you back. The Martinho et al. (2025) review makes it clear that many CrossFit athletes are falling short on carbs and potentially compromising both performance and recovery as a result.
As a coach, trainer, or nutrition professional, helping clients match their nutrition to their training isn’t just about hitting macros but more about understanding the why behind the numbers. And that starts with knowing how different workouts stress the body in different ways.
If you have a keen interest in this area, proper training through nutrition coach courses or broader nutrition courses can make a massive difference in how confidently you support your clients. Because in the end, good training is only half the story. It’s fuel that makes the real difference.
Reference
Martinho, D. V., Rebelo, A., Clemente, F. M., Costa, R., Gouveia, É. R., Field, A., et al. (2025). Nutrition in CrossFit® – scientific evidence and practical perspectives: a systematic scoping review. Journal of the International Society of Sports Nutrition, 22(1), 2509674. Click here to review the full research article.
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