CrossFit nutrition for training, the Open and competition days

At a glance

• Energy systems: Phosphocreatine and glycolytic, plus aerobic base
• Session style: Short, intense, mixed-modal workouts
• Competition format: Multiple scored events across one or more days
• Key risk: Low carbohydrate habits limiting high-intensity output

The physiology of a CrossFit workout

CrossFit workouts blend barbell lifting, gymnastics such as pull-ups and handstand work, and conditioning on rowers, bikes and runs. Many workouts are short and near-maximal, relying on the phosphocreatine system for heavy lifts and on glycolysis for sustained high-intensity efforts. Longer chippers and conditioning pieces add a real aerobic demand, so glycogen stores and recovery between sessions shape how well you perform.

Training volume varies widely. A recreational member may attend a class most days, while competitive athletes commonly train twice a day, combining strength cycles, skill work and conditioning. Each layer adds to total energy and carbohydrate needs. Because workouts are varied and often not programmed far in advance, fuelling has to be flexible rather than a fixed daily plan.

Competition ranges from the online Open, where you complete a workout and submit a score, to on-site competitions with several events across a day or a weekend, sometimes with heats only a short time apart. That format makes recovery between events, gut comfort and easy-to-carry food the defining nutrition challenge for competitive CrossFit athletes.

Nutrition priorities for CrossFit athletes

Enough carbohydrate for intensity

Low-carbohydrate approaches are popular in CrossFit culture but can blunt repeated high-intensity efforts. For around an hour of moderate training a day, evidence suggests 5–7 g/kg/day, with more on double-session days; we personalise this to your programme. [1]

Protein across the day

Heavy lifting and gymnastics volume create ongoing repair needs. Most exercising people do well on 1.4–2.0 g/kg/day, split into servings of 20–40 g every 3–4 hours rather than one large evening meal. [2]

Creatine for strength and power

Creatine supports repeated high-intensity and strength work, which suits CrossFit well. A common protocol is about 20 g/day for 5–7 days, then 3–5 g/day; we check whether it is appropriate for you and choose a batch-tested product. [3]

Refuelling between events

When events are only a few hours apart, carbohydrate of 1.0–1.2 g/kg/h over the first 4 hours speeds glycogen recovery. We turn this into practical, portable snacks for the warm-up area. [1]

Body composition without restriction

Strength-to-weight ratio matters for gymnastics, which can create pressure to diet hard. We focus on fuelling performance and health, and we look out for signs of low energy availability. [4]

Training around work and class times

Early-morning and after-work classes leave little time to eat. We plan simple pre-session snacks and post-session meals that fit your routine.

CrossFit competition-day fuelling

1. Day before: Taper training, eat regular carbohydrate-rich meals and prepare a cool bag with labelled snacks, drinks and recovery options for each gap in the event schedule.
2. Before the first event: Eat a familiar breakfast containing 1–4 g/kg of carbohydrate 1–4 hours before your first heat, adjusting the amount to the time available. If you use caffeine, 3–6 mg/kg about 60 minutes before is the evidence-based range. [1]
3. Between events: If the next event is only a few hours away, aim for 1.0–1.2 g/kg/h of carbohydrate across the gap, using low-fibre options such as rice cakes, bananas, sports drinks or sandwiches, plus fluid to replace sweat losses. [1]
4. After the final event: Have a full meal with about 0.3 g/kg of high-quality protein and plenty of carbohydrate, especially if there is another competition day tomorrow. [1]

General guidance from sports nutrition consensus statements. Your practitioner will tailor amounts to you.

CrossFit athletes and formats

Class-based members

Training most days around work, often fasted in the morning or late in the evening. The focus is consistent meals, enough carbohydrate and protein spread across the day.

The Open and online qualifiers

One workout at a time with the chance to repeat it. Fuelling the attempt and recovering well enough for a re-test later in the week is the priority.

Multi-event competitions

Several workouts in a day, sometimes over several days. Recovery fuelling, gut comfort and practical food logistics decide how well you hold up in the later events.

Masters and team divisions

Masters athletes often have more time pressure and recovery needs, so protein distribution matters. Team events change work-rest patterns, which shifts what you can eat between pieces.

What we help with

• Running out of energy late in longer conditioning workouts
• Following low-carbohydrate trends that hurt high-intensity performance
• Not knowing what to eat between competition heats
• Gut discomfort during burpee, rowing or running-heavy workouts
• Pressure to lean out for gymnastics and bodyweight movements
• Choosing creatine, caffeine and pre-workouts that are batch-tested
• Fuelling twice-daily training around a full-time job

Ongoing support, not one-off sessions

We do not work with athletes on a one-off basis. Sports nutrition works best when it adapts to your training, so we recommend an initial consultation followed by at least three follow-ups.

Who you could work with

• Tom Hill, SENr Sports and Performance Nutritionist
• Jenaed Ruddock, HCPC-registered Sports Dietitian (SENr)
• Beatriz Ribeiro, HCPC-registered Dietitian

Book your consultation

Book an initial consultation or book a free discovery call to talk it through first. All consultations are online.

Explore more

See all the sports we work with, our RED-S nutrition support, or meet the team.

Frequently asked questions

Is a low-carbohydrate diet good for CrossFit?

CrossFit relies heavily on high-intensity efforts that use carbohydrate as their main fuel, so restricting it often reduces the quality of hard workouts. Needs vary with training volume, and we personalise carbohydrate to your sessions rather than applying a blanket rule.

Should CrossFit athletes take creatine?

Creatine is one of the better-supported supplements for repeated high-intensity and strength work, which describes much of CrossFit. We check whether it suits you, discuss loading or a steady daily dose, and recommend batch-tested products such as Informed Sport to reduce contamination risk.

What should I eat between events at a CrossFit competition?

It depends on the gap. With a few hours between heats, regular carbohydrate-rich snacks and fluid help restore glycogen; with a short gap, small portions of easily digested carbohydrate are usually better tolerated. We build a timed plan around your event schedule.

Can you help me improve body composition for CrossFit?

We can support changes in body composition where they are appropriate for your health and performance, but we do not set target weights or body-fat figures. Our priority is fuelling your training adequately, and we screen for signs of low energy availability along the way.

How many consultations will I need?

We do not work with athletes on a one-off basis. CrossFit programming changes week to week, and we need to see how your fuelling holds up across strength cycles, conditioning blocks and competition, so we recommend a minimum of three follow-up consultations after your initial online consultation.

My teenager trains at a CrossFit box. Can you help?

This page is written for adult athletes. Young athletes are supported through our paediatric team, who take growth, development and school commitments into account.

References

1. Thomas DT, Erdman KA, Burke LM. Position of the Academy of Nutrition and Dietetics, Dietitians of Canada, and the American College of Sports Medicine: Nutrition and Athletic Performance. J Acad Nutr Diet. 2016;116(3):501–528.
2. Jäger R, et al. International Society of Sports Nutrition Position Stand: protein and exercise. J Int Soc Sports Nutr. 2017;14:20.
3. Maughan RJ, et al. IOC consensus statement: dietary supplements and the high-performance athlete. Br J Sports Med. 2018;52(7):439–455.
4. Mountjoy M, et al. 2023 International Olympic Committee (IOC) consensus statement on Relative Energy Deficiency in Sport (REDs). Br J Sports Med. 2023;57(17):1073–1097.